Shapley Optical Survey II The effect of environment on the colour-magnitude relation and ga

合集下载

中考英语书面表达议论文论证过程单选题40题

中考英语书面表达议论文论证过程单选题40题1. In a debate, when you start your speech, the first thing you should do is to _____.A. state your opinion clearlyB. give examplesC. quote others' wordsD. ask questions答案：A。

本题考查论点提出的方式。

A 选项“state your opinion clearly”清晰地陈述你的观点，这是在辩论中开始发言时首先应该做的。

B 选项“give examples”举例，通常在后续论证中使用。

C 选项“quote others' words”引用他人的话，不是首先要做的。

D 选项“ask questions”提问，一般不是论点提出的首要动作。

2. When writing an argumentative essay, which of the following is the best way to present your main point at the beginning?A. Telling a story.B. Describing a scene.C. Making a bold statement.D. Listing some data.答案：C。

在写议论文时，C 选项“Making a bold statement”做出大胆的陈述，能直接有效地在开头提出主要观点。

A 选项“Telling a story”讲故事，更多用于引出话题或增加趣味性。

B 选项“Describing a scene”描述场景，并非直接提出论点的好方式。

D 选项“Listing somedata”列举一些数据，常用于论证过程而非开头提出论点。

3. To introduce your argument in an essay, which of the following sentences is the most appropriate?A. Have you ever thought about this problem?B. In my opinion, this is a serious issue.C. Let me tell you a joke first.D. Many people have different ideas.答案：B。

矢量光束Cylindrical vector beams from

Cylindrical vector beams:from mathematical concepts to applications Qiwen ZhanElectro-Optics Graduate Program,University of Dayton,300College Park,Dayton Ohio45469-0245,qiwen.zhan@Received September10,2008;revised November18,2008;accepted November19, 2008;posted November19,2008(Doc.ID101448);published January29,2009 An overview of the recent developments in theﬁeld of cylindrical vectorbeams is provided.As one class of spatially variant polarization,cylindricalvector beams are the axially symmetric beam solution to the full vectorelectromagnetic wave equation.These beams can be generated via differentactive and passive methods.Techniques for manipulating these beams whilemaintaining the polarization symmetry have also been developed.Theirspecial polarization symmetry gives rise to unique high-numerical-aperturefocusing properties thatﬁnd important applications in nanoscale opticalimaging and manipulation.The prospects for cylindrical vector beams and theirapplications in otherﬁelds are also brieﬂy discussed.OCIS codes:140.0140,170.4520,180.0180,240.6680,260.1690,260.5430.1.Introduction (2)2.Mathematical Description of Cylindrical Vector Beams (3)3.Generation of Cylindrical Vector Beams (7)3.1.Active Generation Methods (7)3.2.Passive Generation Methods in Free Space (10)3.3.Passive Generation Methods Using Optical Fiber (13)4.Manipulation of Cylindrical Vector Beams (15)5.Focusing Properties and Applications (18)5.1.Tighter Focusing with Radial Polarization Explained by DipoleRadiation (18)5.2.Numerical Calculation Methods (19)5.3.Tighter Focusing and Applications in Imaging (23)5.4.Three-Dimensional Focus Engineering with Cylindrical VectorBeams (25)5.5.Phase Behavior Near the Focus (31)6.Plasmon Excitation and Focusing with Radial Polarization (37)7.Applications in Optical Trapping (42)8.Applications in Laser Machining (48)9.Summary and Prospects (50)Acknowledgments (51)References (52)Cylindrical vector beams:from mathematical concepts to applications Qiwen Zhan1.IntroductionPolarization is one important property of light.This vector nature of light and its interactions with matter make many optical devices and optical system designs possible.Polarization propagation and interaction with materials have been extensively explored in optical inspection and metrology,display technologies,data storage,optical communications,materials sciences,and astronomy,as well as in biological studies.Most past research dealt with spatially homogeneous states of polarization(SOPs),such as linear,elliptical, and circular polarizations.For these cases,the SOP does not depend on the spatial location in the beam cross section.Recently there has been an increasing interest in light beams with spatially variant SOPs.Spatially arranging the SOP of a light beam,purposefully and carefully,is expected to lead to new effects and phenomena that can expand the functionality and enhance the capability of optical systems.One particular example is laser beams with cylindrical symmetry in polarization,the so-called cylindrical vector(CV) beams.Because of their interesting properties and potential applications,there has been a rapid increase of the number of publications on CV beams.The purpose in the present paper is to provide a review of the recent developments.In Section2,I introduce commonly used mathematical descriptions of these CV beams.Since1972[1,2],various active and passive methods have been developed to generate CV beams.In Section3,an overview of these methods is provided.Manipulation methods that can redirect,rotate,and modulateCV beams are summarized in Section4.CV beams have attracted signiﬁcant recent attention largely because of their unique properties underhigh-numerical-aperture(NA)focusing.In Section5,an intuitive explanation of the focusing properties using electric dipole emission pattern is given,and the numerical computation formula is reviewed.Numerical calculations have shown that tighter focal spots can be obtained by using radial polarization, a subset of CV beams,owing to the existence of a strong and localized longitudinalﬁeld component[3].Such an effect has been experimentallyconﬁrmed by several groups[4–6]and has found applications in high-resolution imaging,plasmonic focusing,and nanoparticle manipulation.The perspectives of CV beam applications in otherﬁelds such as laser machining,remote sensing,terahertz technology,and singular optics will be brieﬂy mentioned toward the end of this paper.2.Mathematical Description of Cylindrical Vector BeamsThe CV beams are vector-beam solutions of Maxwell’s equations that obey axial symmetry in both amplitude and phase [7].Modes with radial andazimuthal polarization are well known in waveguide theory [8].However,their counterparts in free space are less familiar.For free space,the typical paraxial beamlike solutions with harmonic temporal dependence are obtained by solving the scalar Helmholtz equation:ٌ͑2+k 2͒E =0,͑2.1͒where k =2␲/␭is the wavenumber.For a beamlike paraxial solution inCartesian coordinates,the general solution for the electric ﬁeld takes the formE ͑x ,y ,z ,t ͒=u ͑x ,y ,z ͒exp ͓i ͑kz −␻t ͔͒.͑2.2͒By applying the slowly varying envelop approximation ץ2uץz 2 k 2u ,ץ2uץz 2 k ץu ץz ,the Hermite–Gauss solution HG mn modes can be obtained by separation of variables in x and y .Mathematically,these solutions have the following form:u ͑x ,y ,z ͒=E 0H m ͩͱ2xw ͑z ͒ͪH n ͩͱ2y w ͑z ͒ͪw 0w ͑z ͒exp ͓−i ␸mn ͑z ͔͒exp ͫi k2q ͑z ͒r 2ͬ,͑2.3͒where H m ͑x ͒denotes the Hermite polynomials that satisfy the differential equationd 2H mdx 2−2x dH mdx +2mH m =0and E 0is a constant electric ﬁeld amplitude,w ͑z ͒is the beam size,w 0is the beam size at the beam waist,z 0=␲w 02/␭is the Rayleigh range,q ͑z ͒=z −iz 0is the complex beam parameter,and ␸mn ͑z ͒=͑m +n +1͒tan −1͑z /z 0͒is the Gouy phase shift.For m =n =0,this solution reduces to the well-known fundamental Gaussian beam solution:u ͑r ,z ͒=E 0w 0w ͑z ͒exp ͓−i ␸͑z ͔͒exp ͫi k2q ͑z ͒r 2ͬ,͑2.4͒where ␸͑z ͒=tan −1͑z /z 0͒is the Gouy phase shift for the fundamental Gaussian beam.For beamlike paraxial solution in cylindrical coordinates,the solution takes the following general formula:E ͑r ,␾,z ,t ͒=u ͑r ,␾,z ͒exp ͓i ͑kz −␻t ͔͒.͑2.5͒Substituting Eq.(2.5)into the scalar Helmholtz equation (2.1)and applying the slowly varying envelop approximation leads to1r ץץr ͩr ץuץr ͪ+1r 2ץ2uץ␾2+2ik ץuץz =0.͑2.6͒From this equation,the Laguerre–Gauss solution LG pl modes can be obtained by using the separation of variables in r and ␾:u ͑r ,␾,z ͒=E 0ͩͱ2r ␻ͪlL p l ͩ2r 2␻2ͪw 0w ͑z ͒exp ͓−i ␸pl ͑z ͔͒exp ͫi k2q ͑z ͒r 2ͬexp ͑il ␾͒,͑2.7͒where L p l ͑x ͒is the associated Laguerre polynomials that satisfy the differential equationx d 2L p l dx 2−͑l +1−x ͒dL p l dx +pL p l =0and ␸pl ͑z ͒=͑2p +l +1͒tan −1͑z /z 0͒is the Gouy phase shift.For l =p =0,the solution also reduces to the fundamental Gaussian beam solution.For l 0,the LG mode has a vortex phase term e il ␾.Another type of solution of Eq.(2.6)that obeys rotational symmetry (independent of the azimuthal angle ␾)has also been found [9].These solutions take the general formu ͑r ,z ͒=E 0w 0w ͑z ͒exp ͓−i ␸͑z ͔͒exp ͫi k2q ͑z ͒r 2ͬJ 0ͩ␤r 1+iz /z 0ͪexp ͫ−␤2z /͑2k ͒1+iz /z 0ͬ,͑2.8͒where ␤is a constant scale parameter,␸͑z ͒is the Gouy phase shift,z 0is the Rayleigh range,and J 0͑x ͒is the zeroth-order Bessel function of the ﬁrst kind.This group of beamlike solution is the so-called scalar Bessel–Gauss beam solution.When ␤=0,the solution reduces to the fundamental Gaussian beam solution given in Eq.(2.4)as well.The solutions derived above (Hermite–Gauss,Laguerre–Gauss,and Bessel–Gauss)are the paraxial beamlike solutions to the scalar Helmholtz equation (2.1)that correspond to spatially homogeneous polarization or scalar beams.For these beams,the electric ﬁeld oscillation trajectory (i.e.,SOP)does not depend on the location of observation points within the beam cross section.However,if we consider the full vector wave equation for the electric ﬁeld [7],ٌϫٌϫE៝−k 2E ៝=0,͑2.9͒then an axially symmetric beamlike vector solution with the electric ﬁeld aligned in the azimuthal direction should have the form E ៝͑r ,z ͒=U ͑r ,z ͒exp ͓i ͑kz −␻t ͔͒e ៝␾,͑2.10͒where U ͑r ,z ͒satisﬁes the following equation under the paraxial and slowly varying envelope approximation:1r ץץr ͩr ץUץr ͪ−Ur 2+2ik ץUץz =0.͑2.11͒There is a clear difference in the second terms of Eqs.(2.6)and (2.11).The solution that obeys azimuthal polarization symmetry has the trial solutionU ͑r ,z ͒=E 0J 1ͩ␤r 1+iz /z 0ͪexp ͫ−i ␤2z /͑2k ͒1+iz /z 0ͬu ͑r ,z ͒,͑2.12͒where u ͑r ,z ͒is the fundamental Gaussian solution given in Eq.(2.4)and J 1͑x ͒is the ﬁrst-order Bessel function of the ﬁrst kind.This solution corresponds to an azimuthally polarized vector Bessel–Gauss beam solution.Similarly,there should exist a transverse magnetic ﬁeld solutionH ៝͑r ,z ͒=−H 0J 1ͩ␤r 1+iz /z 0ͪexp ͫ−i ␤2z /͑2k ͒1+iz /z 0ͬu ͑r ,z ͒exp ͓i ͑kz −␻t ͔͒h ជ␾,͑2.13͒where H 0is a constant magnetic ﬁeld amplitude and h ជ␾is the unit vector in the azimuthal direction.For this azimuthal magnetic ﬁeld solution,thecorresponding electric ﬁeld in the transverse plane is aligned in the radial direction.Hence Eq.(2.13)represents the radial polarization for the electric ﬁeld.Clearly there should be a z component of the electric ﬁeld as well.However,this component is weak and can be ignored under paraxial conditions.For comparison,examples of the spatial distributions of the instantaneouselectric ﬁeld vector for several linearly polarized Hermite–Gauss and Laguerre–Gauss modes and the CV modes are illustrated together in Fig.1.The SOPs of the modes shown in Figs.1(a)–1(f)are considered spatially homogeneous,although the electric ﬁeld may have an opposite instantaneous direction caused by the inhomogeneous phase distribution across the beam.The ﬁeld illustrated in Fig.1(g)has polarization aligned in the radial direction.This is called the radial polarization.Similarly,the polarization pattern shown inFig.1(h)is called the azimuthal polarization.The generalized CV beams shown in Fig.1(i)are a linear superposition of these two.Due to the transverse ﬁeld continuity,one of the features of these CV modes is the existence of a null of the transverse ﬁeld.In many applications,instead of the vector Bessel–Gauss solutions derived above,other simpliﬁed distributions have been used,especially for CV beams with large cross sections.For very small ␤,the vector Bessel–Gauss beam at the beam waist can be approximated asE ៝͑r ,z ͒=Ar exp ͩ−r 2w 2ͪe ៝i ,i =r ,␾.͑2.14͒The amplitude proﬁle is exactly the LG 01mode [10]without the vortex phase term exp ͑i ␾͒.Using Eqs.(2.3)and (2.7),it is easy to show that CV beams can also be expressed as the superposition of orthogonally polarized Hermite–Gauss HG 01and HG 10modes [11]:E ៝r =HG 10e ៝x +HG 01e៝y ,͑2.15͒E ៝␾=HG 01e ៝x +HG 10e ៝y ,͑2.16͒where E r and E ␾denote radial and azimuthal polarization,respectively.This is illustrated schematically in Fig.2.For some applications,particularly for those involving the generation of collimated CV beams through passivedevices in applications requiring high-NA focusing,annular distributions withthe center blocked by an opaque stop have also been frequently used.The ﬁeld after these devices or in the pupil plane is [12]E ៝͑r ͒=P ͑r ͒e ៝i ,i =r ,␾,͑2.17͒where P ͑r ͒is the beam cross section or pupil function.For uniform annular illumination,P ͑r ͒=ͭ1,r 1Ͻr Ͻr 20,0Ͻr Ͻr 1.͑2.18͒Spatial distribution of instantaneous electric vector ﬁeld for several conventional modes and CV modes:(a)x -polarized fundamental Gaussian mode;(b)x -polarized HG 10mode;(c)x -polarized HG 01mode;(d)y -polarized HG 01mode;(e)y -polarized HG 01mode;(f)x -polarized LG 01mode;(g)radially polarized mode;(h)azimuthally polarized mode;(i)generalized CV beams as a linear superposition of (g)and (h).3.Generation of Cylindrical Vector BeamsSince 1972,many methods of generating CV beams have been reported,especially in the past decade or so.Depending on whether the generation methods involve amplifying media,these methods can be categorized as active or passive.3.1.Active Generation MethodsT ypically,active methods involve the use of laser intracavity devices that force the laser to oscillate in CV modes.Intracavity devices can be axialbirefringent (intrinsic birefringent,form birefringent,or induced birefringent)component or axial dichroic component to provide mode discrimination against the fundamental mode.One of the earliest experiments utilized an intracavity axial birefringent component [1].In this setup (Fig.3),a calcite crystal is placed in a telescope setup with its crystal axis parallel to the optical axis of the cavity.Because of double refraction,the e polarization and o polarization experience slightly different magniﬁcations.With a central stop aperture,one polarization is discriminated more because of higher loss.The cylindrical symmetry of the entire system ensures that the oscillation mode has cylindrical polarization symmetry.Since calcite is negatively birefringent,the azimuthal polarization was generated directly in this setup.Radialpolarization was generated with optical active materials (quartz)to rotate the electric ﬁeld by 90°.It is important to have the optical axis of the lasing medium aligned with the optical axis of the resonator if the laser medium is also anisotropic.Other papers extended these early reports [13,14].However,owing to the lack of practical applications of these special polarization modes,little attention was paid to this ﬁeld until recently.Formation of radial and azimuthal polarizations using linear superposition of orthogonally polarized HG modes.Driven by the potential applications of CV beams in imaging,machining,particle trapping,data storage,remote sensing,etc.,this ﬁeld has seen rapidly growth in the past decade or so.Active CV beam generation was revisited,and new methods were developed.For examples,CV beam generation with axial intracavity birefringence was reinvented and improved [15–17].Besides axial birefringence,axial intracavity dichroism created with conical axicon[18]and Brewster angle reﬂectors [19,20]were also utilized to provide polarization mode selection.One such conﬁguration [20]is illustrated in Fig.4.The techniques mentioned above used bulk intracavity devices for creating axial birefringence or dichroism.The recent availability of microfabrication and nanofabrication tools enables the creation of diffractive phase plate orpolarization selective end mirror devices [14,21]for CV beam generation (Fig.5).This type of device allows a much more compact laser design and can be exploited to generate high output power.In addition to those methods that utilize either intracavity axial birefringence or dichroism to provide the necessary mode discrimination,CV beamscan also be generated with intracavity interferometric methods using folded mirrors or prisms based on the linear superposition principle given by Eqs.(2.15)and (2.16).A recently proposed intracavity Sagnac interferometerCalciteAperture+Stop Mirror Diagram of a ruby laser that generates CV beam output.The optical axis of the calcite crystal is parallel to the resonator axis.The combination of the calcite crystal,the telescope,and the aperture and stop provides the mode discrimination to force the laser operation in CV polarization mode.Figure adapted with permission from[1].©1972American Institute of Physics.4CBPLD pumpedNd:YAG rodSiO 2Nd:Y AG laser that generates CV beams by using axial dichroism created by a conical Brewster prism (CBP).The structure of the conical Brewster prism is shown to the right.Figure adapted with permission from [20].setup [22]is illustrated in Fig.6.In this example,linearly polarized HG 01modes are created by placing a thin wire across the center of the cavity.A dove prism provides the necessary rotation to create the orthogonally polarized HG 10and HG 01modes.The Sagnac interferometer combines the two modes and creates the CV output.Active mediumYb:YAG (thin disk)couplermirrorYb:Y AG thin-disk laser that generates CV beam outputs using a circular multilayer polarizing grating end mirror.The output beam proﬁle andpolarization pattern are shown to the right.Figure adapted with permissionfrom [21].6Diagram of a laser cavity design with Sagnac interferometer as an end mirror to create CV beam output.BS,beam splitter.Figure reprinted with permission from [22].3.2.Passive Generation Methods in Free SpacePassive methods have also been used to generate CV beams in free space.In general,these methods convert those more commonly known spatially homogeneous polarizations(typically linear or circular polarization)into spatially inhomogeneous CV polarizations.Consequently,devices with spatially variant polarization properties are normally required.For example,axial birefringence and dichroism have been applied to generate CV beam outside the laser cavity.Simple setups with a radial analyzer made either from birefringent materials[23]or from dichroic materials[24]can be used to generate the CV beams.A radial analyzer is a device that has its local polarization transmission axis aligned along either the radial or the azimuthal directions.In general,birefringent radial analyzers have better polarization purity than dichroic radial analyzers,while the setup for a dichroic radial analyzer is more compact.A circularly polarized collimated beam needs to be used as the input to the radial analyzer.The beam after the radial analyzerwill be polarized either radially or azimuthally,depending on the type of radial analyzer used.However,one important factor that requires caution is the Berry’s phase[24].For a circularly polarized input,theﬁeld can be expressed asE៝in=e៝x+je៝y=͑cos␾e៝r−sin␾e៝␾͒+j͑sin␾e៝r+cos␾e៝␾͒=e j␾͑e៝r+je៝␾͒,͑3.1͒where e៝x and e៝y are the unit vectors in Cartesian coordinates and e៝r and e៝␾are the unit vectors in the polar coordinate system.After the beam passes through the radial analyzer,since the transmission axis of the radial analyzer is aligned along the radial direction,the SOP becomesE៝out=e j␾e៝r.͑3.2͒This indicates that,although the electricalﬁeld is aligned along the radial direction,there is a spiral phase factor on top of it.The geometric spiral phase has been conﬁrmed by interferometric measurement (Fig.7)[24].To obtain a true CV beam,a spiral phase element(SPE)withthe opposite helicity is necessary to compensate for the geometric phase(Fig.8).A SPE can be fabricated with a variety of lithographic techniques,suchas electron-beam lithography and gray-scale lithography,or can be generated by a liquid crystal(LC)spatial light modulator(SLM).An interestingsimple tunable SPE using a deformed cracked glass plate was reported in[25]. Commercial SPE products are available now at several vendors[26].This generation method has been successfully implemented by several groups to generate both continuous wave(CW)and ultrafast CV beams[6,27,28]. Spatially variant polarization rotation can also be utilized to produce CV beams. In this case,linearly polarized light is typically used as input and thenlocally rotated to the desired spatial polarization pattern.One such example is a device with twisted nematic LC sandwiched between linearly and circularly rubbed plates[29,30].Owing to the circular rubbing of the second plate,the twisted nematic LC molecules continuously rotate from the initial linear rubbing direction to the corresponding spatially distributed rubbing direction on the other plate.An incident beam that is linearly polarized perpendicular or parallel to the linear rubbing direction will follow themolecules’rotation,creating a radial or azimuthal polarization on the exiting side.A ␲-step phase plate is necessary to correct a geometric phase similar to what we mentioned above.These types of devices are already available at several vendors [31].Another very popular and powerful passive method uses a LC SLM.Despite its relatively high cost,a LC SLM offers the ﬂexibility and capability to generate an almost arbitrary complex ﬁeld distribution.One such example is shown in Fig.9[32].In this setup,two LC SLMs were used.The ﬁrst SLM provides pure phase modulation to the incoming beam to either correct certain aberrations in the system or to add the desired phase pattern to the beam.The combination of the ␭/4plate and the second SLM essentially forms a polarization rotator[23,33],where the amount of rotation is determined by the phase retardation of each pixel on the SLM.Properly designing the phase pattern on the second He‐Ne beam Beam splitter λ/4plateanalyzer Mach–Zehnder interferometer setup to verify the spiral Berry’s phase given in Eq.(3.2).The Berry’s phase is shown in the lower right-hand corner.8λ/2plate λ/2plateSPE Radialanalyzer Cylindrical vectoroutputGeneration of CV beam using radial analyzer and SPE.A circularly polarized input is used.The cascaded two ␭/2plates rotate the polarization to the desired pattern.SLM allows the input linear polarization to be converted into any arbitrary polarization distribution,including CV beams.Besides spatially variant polarization rotation,another class of methods use spatially variant retardation axis arrangements.For example,for a linearpolarization input,␭/2plates with spatially variant fast axis directions can be used to convert the linear polarization into CV polarizations.This can be achieved by taping or gluing together several segmented ␭/2plates with different discrete crystal angles (Fig.10)[34].Because of the discreteness,this type of device provides only rough spatial alignment of the polarization.A mode selector can be used to further clean up the polarization distribution pattern.One example is shown in Fig.11[4].The polarization is initially roughly aligned by four segmented ␭/2plates.Then a near-confocal Fabry–Perot interferometer is used to ﬁlter out the undesired mode and keep the radialf 1f 2SLM 2φxyθxyA polarization mode converter setup with two SLMs.The ﬁrst SLM creates the desired phase pattern.The combination of the ␭/4plate and the secondreﬂection-type SLM converts the beam into the spatially variant polarization pattern.The second SLM can be programed to convert a linearly polarized beam into CV beam.Figure adapted with permission from [32].10Segmented spatially variant ␭/2plates that can convert linear polarization into CV polarization.Figure reprinted from [34]with permission from Elsevier.polarization component.Recently,continuous rotation of linear polarization input using stress-induced space-variant plate [35]and photoaligned LC polymers [36]were reported,eliminating the need for a mode selector.For circularly polarized input,a spatially variant ␭/4retarder with axially symmetric local axis arrangement can be used to convert the input intocylindrical polarization.This type of device can be realized with spatial-variant subwavelength gratings (Fig.12)[37].The form birefringence of thesubwavelength grating provides ␭/4retardation,and its local orientation is continuously varied through lithographic patterning.However,owing to the requirement of a subwavelength period,extension into the visible and UV would be difﬁcult.An interesting technique using a transparent electro-optic (EO)ceramic [Pb ͑Mg 1/3Nb 2/3͒O 3−PbTiO 3,PMN-PT]as a radial polarization retarder (Fig.13,EO-RPR)was reported recently [38].A voltage is applied across the electrodes to create ␭/4retardation with a radially aligned retardation axis.This technique in principle could provide tunable CV generation from 500to 7000nm,depending on the applied voltage.However,in both cases a geometrical spiral phase exists and needs to be compensated.In addition to the methods using the spatially variant polarization properties described above,interferometric methods have also been used to create CV beams in free space.Methods using a Mach–Zehnder interferometercombined with a spiral phase plate [39]or a spiral phase created by a LC SLM[5]have been developed.A simple technique using ␲-phase step plates was reported in [40].Recently a common path interferometer implemented with a LC SLM to generate CV beams and other more complex vector beams was also demonstrated (Fig.14)[41].3.3.Passive Generation Methods Using Optical FiberGeneration of CV beams with few-mode ﬁber is another technique that deserves special attention.It is known that a multimode step-index optical ﬁber can support the TE 01and TM 01annular modes possessing cylindrical polarization symmetry,with the TE 01mode being azimuthally polarized and the TM 01Experimental setup that uses a segmented ␭/2plates polarization converter and a near-confocal Fabry–Perot interferometer (NCFPI)as a mode selector to generate CV beams.OD,optical diode;HWP ,half-wave plate;PH,pinhole;TL1,TL2,telescope lenses;PC,polarization converter;FL,focusing lens;CL,collimating lens;M,four mirrors;MD,monitor diode;AS,aperture stop;MO,microscope objective;PD,photodiode.Figure reprinted with permission from [4](/abstract/PRL/v91/i23/e233901).©2003American Physical Society.mode being radially polarized (Fig.15).Under the weakly guidingapproximation,these modes have the same cutoff parameter that is lower than all the other modes except the HE 11fundamental mode.In general,it is difﬁcult to excite these modes in an optical ﬁber without exciting the fundamental mode.The presence of a strong fundamental mode would spoil the cylindrical polarization purity.CV mode excitation in ﬁber can be achieved with careful misalignment between a single-mode and amultimode ﬁber [42].However,the conversion efﬁciency is fairly low for this method.The efﬁciency can be improved by preforming the incidentpolarization either in phase or polarization [27,43].A laboratory picture for CV mode excitation using an SPE is shown in Fig.16.A collimated laser beam passes through a SPE.Then it is coupled into a ﬁber that is carefully chosen such that it supports only the fundamental mode and the second-higher-order modes.The optical ﬁber acts as a spatial ﬁlter and a polarization modeselector.The polarization symmetry is conﬁrmed by inserting a linear polarizer between the ﬁber output end and the observation plane (shown in Fig.16).Using optical ﬁber as mode selector,a tunable and narrow band CV beam laser source was demonstrated in [44].(a)Geometry of spatially variant subwavelength grating.A scanning electron microscope image of the device is also shown.Experimentally measured spatial polarization patterns for (b)right-hand circular polarization and (c)left-hand circular polarization are illustrated.Figure reprinted with permission from [37].4.Manipulation of Cylindrical Vector Beams To make use of the CV beams in different applications,devices that can perform basic manipulations such as reﬂection,polarization rotation,and retardation are necessary.The key for these operations is to maintain thepolarization symmetry.When CV beams are reﬂected and steered,polarization symmetry could be broken owing to the nonequal reﬂection coefﬁcients for s and p polarizations.Even if the magnitudes of these reﬂection coefﬁcients are close,the phase difference can still destroy the polarization symmetry.In principle,metallic mirrors should preserve the polarization symmetry better.However,many metallic mirrors have protective coatings that could give rise to different reﬂection coefﬁcients for s and p bination oftwo identical beam splitters (picked up from the same coating run)with twistedLG01generation SPEλ/2platesAn experimental setup using an EO radial polarization retarder (EO-RPR)to generate CV beams.Figure adapted with permission from [38].14A common-path interferometer setup implemented with a SLM to generate CV beams and other more complicated vector beams.Several CV beams with different polarization patterns are also shown to the right.Figure reprinted with permission from [41].。

刺激-反应联结学习在项目特异性比例一致效应中的作用

327
效应。研究者认为，可能存在局部的、项目特异性的认知控制机制，可以根据单个项目的比例偏置情况选择性地进行注意资源分配从而影响不同项目的反应（Jacoby et al., 2003）。
然而，注意调节理论近来受到了其他研究的挑战（Schmidt & Besner, 2008; Schmidt & Lemercier, 2019）。Schmidt 和 Besner 认为，ISPC 效应中比例一致性与刺激–反应的可能性混合在一起，可以用更经济的可能性学习来解释这一效应。该研究提出了可能性学习假说（contingency learning hypothesis），表示认知控制不是必要的，被试完全可以通过学习发现刺激无关维度与正确反应的可能性关系，并基于此预测正确的反应。在冲突任务中，一致试次占多数时，刺激常常伴随着一致的任务无关的刺激属性，这一属性有很大可能性可以去预测正确的反应，而多数试次为不一致时，被试可能根据伴随的不一致的任务无关刺激属性去预测反应（Schmidt & Lemercier, 2019）。这一策略可以加快一致或不一致试次的反应，从而产生 ISPC 效应。可能性学习假说基于刺激–反应（stimulus-response, S-R）之间的联结解释了 ISPC 效应，是 S-R 联结学习的一种方式（Schmidt, 2013）。
心理与行为研究 2021，19(3)：326~333 Studies of Psychology and Behavior
刺激–反应联结学习在项目特异性比例一致效应中的作用 *
夏天生1 谭玲2
(1 广东工业大学艺术与设计学院，广州 510090) (2 广东工业大学管理学院，广州 510520)

优美斯（Optimax Systems）的相位平移干扰光学测量方法白皮书说明书

The Effect Of Phase Distortion On InterferometricMeasurements Of Thin Film Coated Optical SurfacesJon Watson, Daniel SavageOptimax Systems, 6367 Dean Parkway, Ontario, NY USA*********************©Copyright Optimax Systems, Inc. 2010This paper discusses difficulty in accurately interpreting surface form data from a phase shifting interferometer measurement of a thin film interference coated surfaces.PHASE-SHIFTING INTERFEROMETRYPhase-shifting interferometry is a metrology tool widely used in optical manufacturing to determine form errors of an optical surface. The surface under test generates a reflected wavefront that interferes with the reference wavefront produced by the interferometer 1. A phase-shifting interferometer modulates phase by slightly moving the reference wavefront with respect to the reflected test wavefront 2 . The phase information collected is converted into the height data which comprises the surface under test3.Visibility of fringes in an interferometer is a function of intensity mismatch between the test and reference beams. Most commercially available interferometers are designed to optimize fringe contrast based on a 4% reflected beam intensity. If the surface under test is coated for minimum reflection near or at the test wavelength of the interferometer, the visibility of the fringe pattern can be too low to accurately measure.OPTICAL THIN-FILM INTERFERENCE COATINGSOptical thin-film interference coatings are structures composed of one or more thin layers (typically multiples of a quarter-wave optical thickness) of materials deposited on the surface of an optical substrate.The goal of interference coatings is to create a multilayer film structure where interference effects within the structure achieve a desired percent intensity transmission or reflection over a given wavelength range.The purpose of the coating defines the design of the multilayer structure. Basic design variables include:• Number of layers• Thickness of each layer• Material of each layerThe most common types of multilayer films are high reflector (HR) and anti-reflection (AR) coatings. HR coatings function by constructively interfering reflected light, while AR coatings function by destructively interfering reflected light. These coatings are designed to operate over a specific wavelength range distributed around a particular design wavelength.To produce the desired interference effects, thin-film structures are designed to modulate the phase of the reflected or transmitted wavefront. The nature of the interference effect depends precisely on the thickness of each layer in the coating as well as the refractive index of each layer. If the thickness and index of each layer is uniform across the coated surface, the reflected wavefront will have a constant phase offset across the surface. However, if layer thicknesses or index vary across the coated surface, then the phase of thereflected wavefront will also vary. Depending on the design of the coating and the severity of the thickness or index non-uniformity, the distortion of the phase of the reflected wavefront can be severe. 4Layer thickness non-uniformity is inherent in the coating process and is exaggerated by increasing radius of curvature of the coated surface.5 All industry-standard directed source deposition processes (thermal evaporation, sputtering, etc) result in some degree of layer thickness non-uniformity.5 Even processes developed to minimize layer non-uniformity, such as those used at Optimax, will still result in slight layer non-uniformity (within design tolerance).TESTING COATED OPTICS INTERFEROMETRICALLYPhase-shifting interferometers use phase information to determine the height map of the surface under test. However, surfaces coated with a thin-film interference coating can have severe phase distortion in the reflected wavefront due to slight layer thickness non-uniformities and refractive index inhomogeneity. Therefore, the measured irregularity of a coated surface measured on a phase shifting interferometer at a wavelength other than the design wavelength, may not represent the actual irregularity of the surface. Even using a phase shifting interferometer at the coating design wavelength does not guarantee accurate surface irregularity measurements. If a coating has very low reflectance over any given wavelength range (such as in the case of an AR coating), the phase shift on reflection with wavelength will vary significantly in that range.7 Figure 1 shows an example of how the phase can vary with coating thickness variations.Figure 1In this particular case, if a point at the lens edge has the nominal coating thickness and the coating at lens center is 2% thicker, expect ~38° phase difference in the measurement (~0.1 waves). This will erroneous be seen as height by the interferometer, despite the actual height change in this case being less than 7nm (~0.01 waves). Also, depending on coating design, low fringe visibility may inhibit measurements.There is an extreme method to determine the irregularity of a thin-film interference coated surface by flash coating it with a bare metal mirror coating. A metal mirror coating is not a thin-film interference coating, and the surface of the mirror represents the true surface, This relatively expensive process requires extra time, handling, and potential damage during the metal coating chemical strip process.CONCLUSIONS•There can be practical limitations to getting accurate surface form data on coated optical surfaces due to issues with phase distortion and fringe visibility.•The issues are a function of thin film coating design particulars and the actual deposition processes.1 R.E. Fischer, B. Tadic-Galeb, P. Yoder, Optical System Design, Pg 340, McGraw Hill, New York City, 20082 H.H. Karow, Fabrication Methods For Precision Optics, Pg 656, John Wiley & Sons, New York City, 19933 MetroPro Reference Guide OMP-0347J, Page 7-1, Zygo Corporation, Middlefield, Connecticut, 20044 H.A. Macleod, Thin Film Optical Filters, Chapter 11: Layer uniformity and thickness monitoring, The Institute of Physics Publishing, 2001.5 R.E. Fischer, B. Tadic-Galeb, P. Yoder, Optical System Design, Pg 581, McGraw Hill, New York City, 2008。

大学-光学的培训教材

2
Historical Overview
Discover the milestones and key discoveries that have shaped the field of optics throughout history.
3
Modern Applications
Learn about the wide range of modern applications of optics, from telecommunications to imaging technology.
Endoscopy
Learn how fiber optics enables minimally invasive procedures and allows doctors to visualize internal organs.
Polarization of Light
1 Polarizing Filters
Future Trends in Optics
Quantum Optics
Explore the emerging field of quantum optics and its revolutionary applications in computing, communication, and cryptography.
Diagnostic Imaging Laser Surgery
Discover how optics plays a vital role in medical imaging techniques like X-rays, CT scans, and MRI.
Explore the use of lasers in various surgical procedures, including laser eye surgery and skin treatments.

TPO38托福阅读答案解析

1. According to paragraph 1, what happens to the light when a specimen is being viewed with a light microscope?A. The light continues unchanged directly into the viewer's eye or onto film.B. A glass lens bends the light to form a magnified image of the specimen.C. The light is projected onto photographic film to produce a blurred image.D. The intensity of the light increases a thousand times.Paragraph 1 is marked with ►答案：B 选项正确解析：本题根据 the light，specimen 和a light microscope 定位到第一段这几句：The first microscopes were light microscopes, which work by passing visible light through a specimen. Glass lenses in the microscope bend the light to magnify the image of the specimen and project the image into the viewer's eye or onto photographic film. 第二句讲了光学显微镜的原理，就是折射光以放大标本的图像，并且把图像投射到观察者的眼睛里或者投射到胶卷上。

选项 B 符合这句话的前半句，正确。

AXIS P1465-LE 2 MP 全能防盗摄像头说明书

DatasheetAXIS P1465-LE Bullet CameraFully featured,all-around2MP surveillanceBased on ARTPEC-8,AXIS P1465-LE delivers excellent image quality in2MP.It includes a deep learning processing unit enabling advanced features and powerful analytics based on deep learning on the edge.With AXIS Object Analytics, it can detect and classify humans,vehicles,and types of vehicles.Available with a wide or tele lens,this IP66/IP67, NEMA4X,and IK10-rated camera can withstand winds up to50m/s.Lightfinder2.0,Forensic WDR,and OptimizedIR ensure sharp,detailed images under any light conditions.Furthermore,Axis Edge Vault protects your Axis device ID and simplifies authorization of Axis products on your network.>Lightfinder2.0,Forensic WDR,OptimizedIR>Analytics with deep learning>Audio and I/O connectivity>Built-in cybersecurity features>Two lens alternativesAXIS P1465-LE Bullet Camera CameraModels AXIS P1465-LE9mmAXIS P1465-LE29mmImage sensor1/2.8”progressive scan RGB CMOSPixel size2.9µmLens Varifocal,remote focus and zoom,P-Iris control,IR correctedAXIS P1465-LE9mm:Varifocal,3-9mm,F1.6-3.3Horizontal field of view117˚-37˚Vertical field of view59˚-20˚Minimum focus distance:0.5m(1.6ft)AXIS P1465-LE29mm:Varifocal,10.9-29mm,F1.7-1.7Horizontal field of view29˚-11˚Vertical field of view16˚-6˚Minimum focus distance:2.5m(8.2ft)Day and night Automatic IR-cut filterHybrid IR filterMinimum illumination 0lux with IR illumination on AXIS P1465-LE9mm: Color:0.06lux,at50IRE F1.6 B/W:0.01lux,at50IRE F1.6 AXIS P1465-LE29mm: Color:0.06lux,at50IRE F1.7 B/W:0.01lux,at50IRE F1.7Shutter speed With Forensic WDR:1/37000s to2sNo WDR:1/71500s to2sSystem on chip(SoC)Model ARTPEC-8Memory1024MB RAM,8192MB Flash ComputecapabilitiesDeep learning processing unit(DLPU) VideoVideo compression H.264(MPEG-4Part10/AVC)Baseline,Main and High Profiles H.265(MPEG-H Part2/HEVC)Main ProfileMotion JPEGResolution16:9:1920x1080to160x9016:10:1280x800to160x1004:3:1280x960to160x120Frame rate With Forensic WDR:Up to25/30fps(50/60Hz)in all resolutions No WDR:Up to50/60fps(50/60Hz)in all resolutionsVideo streaming Up to20unique and configurable video streams aAxis Zipstream technology in H.264and H.265Controllable frame rate and bandwidthVBR/ABR/MBR H.264/H.265Low latency modeVideo streaming indicatorSignal-to-noiseratio>55dBWDR Forensic WDR:Up to120dB depending on sceneMulti-viewstreamingUp to8individually cropped out view areasNoise reduction Spatial filter(2D noise reduction)Temporal filter(3D noise reduction)Image settings Saturation,contrast,brightness,sharpness,white balance,day/night threshold,exposure mode,exposure zones,defogging,compression,orientation:auto,0°,90°,180°,270°includingcorridor format,mirroring of images,dynamic text and imageoverlay,polygon privacy masks,barrel distortion correctionScene profiles:forensic,vivid,traffic overviewAXIS P1465-LE29mm:Electronic image stabilization Image processing Axis Zipstream,Forensic WDR,Lightfinder2.0,OptimizedIR Pan/Tilt/Zoom Digital PTZ,digital zoomAudioAudio features AGC automatic gain controlNetwork speaker pairing Audio streaming Configurable duplex:One-way(simplex,half duplex)Two-way(half duplex,full duplex)Audio input10-band graphic equalizerInput for external unbalanced microphone,optional5Vmicrophone powerDigital input,optional12V ring powerUnbalanced line inputAudio output Output via network speaker pairingAudio encoding24bit LPCM,AAC-LC8/16/32/44.1/48kHz,G.711PCM8kHz,G.726ADPCM8kHz,Opus8/16/48kHzConfigurable bit rateNetworkNetworkprotocolsIPv4,IPv6USGv6,ICMPv4/ICMPv6,HTTP,HTTPS b,HTTP/2,TLS b,QoS Layer3DiffServ,FTP,SFTP,CIFS/SMB,SMTP,mDNS(Bonjour),UPnP®,SNMP v1/v2c/v3(MIB-II),DNS/DNSv6,DDNS,NTP,NTS,RTSP,RTP,SRTP/RTSPS,TCP,UDP,IGMPv1/v2/v3,RTCP,ICMP,DHCPv4/v6,ARP,SSH,LLDP,CDP,MQTT v3.1.1,Syslog,Link-Localaddress(ZeroConf)System integrationApplicationProgrammingInterfaceOpen API for software integration,including VAPIX®,metadataand AXIS Camera Application Platform(ACAP);specifications at/developer-community.ACAP includes Native SDK andComputer Vision SDK.One-click cloud connectionONVIF®Profile G,ONVIF®Profile M,ONVIF®Profile S andONVIF®Profile T,specification at VideomanagementsystemsCompatible with AXIS Companion,AXIS Camera Station,videomanagement software from Axis’Application DevelopmentPartners available at /vmsOnscreencontrolsAutofocusDay/night shiftDefoggingVideo streaming indicatorWide dynamic rangeIR illuminationPrivacy masksMedia clipAXIS P1465-LE29mm:Electronic image stabilizationEvent conditions ApplicationDevice status:above operating temperature,above or belowoperating temperature,below operating temperature,withinoperating temperature,IP address removed,new IP address,network lost,system ready,ring power overcurrent protection,live stream activeDigital audio input statusEdge storage:recording ongoing,storage disruption,storagehealth issues detectedI/O:digital input,manual trigger,virtual inputMQTT:subscribeScheduled and recurring:scheduleVideo:average bitrate degradation,day-night mode,tampering Event actions Audio clips:play,stopDay-night modeI/O:toggle I/O once,toggle I/O while the rule is activeIllumination:use lights,use lights while the rule is activeMQTT:publishNotification:HTTP,HTTPS,TCP and emailOverlay textRecordings:SD card and network shareSNMP traps:send,send while the rule is activeUpload of images or video clips:FTP,SFTP,HTTP,HTTPS,networkshare and emailWDR modeBuilt-ininstallation aidsPixel counter,remote zoom(3x optical),remote focus,autorotationAnalyticsAXIS ObjectAnalyticsObject classes:humans,vehicles(types:cars,buses,trucks,bikes)Trigger conditions:line crossing,object in area,time in area BETAUp to10scenariosMetadata visualized with trajectories and color-coded boundingboxesPolygon include/exclude areasPerspective configurationONVIF Motion Alarm eventMetadata Object data:Classes:humans,faces,vehicles(types:cars,buses, trucks,bikes),license platesConfidence,positionEvent data:Producer reference,scenarios,trigger conditions Applications IncludedAXIS Object AnalyticsAXIS Live Privacy Shield,AXIS Video Motion Detection,activetampering,shock detectionSupportedAXIS Perimeter Defender,AXIS Speed Monitor cSupport for AXIS Camera Application Platform enablinginstallation of third-party applications,see /acap ApprovalsProduct markings CSA,UL/cUL,BIS,UKCA,CE,KC,EACSupply chain TAA compliantEMC CISPR35,CISPR32Class A,EN55035,EN55032Class A,EN50121-4,EN61000-3-2,EN61000-3-3,EN61000-6-1,EN61000-6-2Australia/New Zealand:RCM AS/NZS CISPR32Class ACanada:ICES-3(A)/NMB-3(A)Japan:VCCI Class AKorea:KS C9835,KS C9832Class AUSA:FCC Part15Subpart B Class ARailway:IEC62236-4Safety CAN/CSA C22.2No.62368-1ed.3,IEC/EN/UL62368-1ed.3,IEC/EN62471risk group exempt,IS13252Environment IEC60068-2-1,IEC60068-2-2,IEC60068-2-6,IEC60068-2-14, IEC60068-2-27,IEC60068-2-78,IEC/EN60529IP66/IP67,IEC/EN62262IK10,NEMA250Type4X,NEMA TS2(2.2.7-2.2.9) Network NIST SP500-267CybersecurityEdge security Software:Signed firmware,brute force delay protection,digest authentication,password protection,AES-XTS-Plain64256bitSD card encryptionHardware:Secure boot,Axis Edge Vault with Axis device ID,signed video,secure keystore(CC EAL4+certified hardwareprotection of cryptographic operations and keys)Network security IEEE802.1X(EAP-TLS)b,IEEE802.1AR,HTTPS/HSTS b,TLSv1.2/v1.3b,Network Time Security(NTS),X.509Certificate PKI,IP address filteringDocumentation AXIS OS Hardening GuideAxis Vulnerability Management PolicyAxis Security Development ModelAXIS OS Software Bill of Material(SBOM)To download documents,go to /support/cybersecu-rity/resourcesTo read more about Axis cybersecurity support,go to/cybersecurityGeneralCasing IP66/IP67-,NEMA4X-,and IK10-rated casingPolycarbonate blend and aluminiumColor:white NCS S1002-BFor repainting instructions,go to the product’s supportpage.For information about the impact on warranty,go to/warranty-implication-when-repainting.Power Power over Ethernet IEEE802.3af/802.3at Type1Class3Typical:7.9W,max12.95W10–28V DC,typical7.2W,max12.95WConnectors Network:Shielded RJ4510BASE-T/100BASE-TX/1000BASE-TAudio:3.5mm mic/line inI/O:Terminal block for1alarm input and1output(12V DCoutput,max.load25mA)Power:DC inputIR illumination OptimizedIR with power-efficient,long-life850nm IR LEDsAXIS P1465-LE9mm:Range of reach40m(131ft)or more depending on the sceneAXIS P1465-LE29mm:Range of reach80m(262ft)or more depending on the scene Storage Support for microSD/microSDHC/microSDXC cardRecording to network-attached storage(NAS)For SD card and NAS recommendations see Operatingconditions-40°C to60°C(-40°F to140°F)Maximum temperature according to NEMA TS2(2.2.7):74°C(165°F)Start-up temperature:-40°CHumidity10–100%RH(condensing)Storageconditions-40°C to65°C(-40°F to149°F)Humidity5-95%RH(non-condensing)DimensionsØ132x132x280mm(Ø5.2x5.2x11.0in)Effective Projected Area(EPA):0.022m2(0.24ft2)Weight With weather shield:1.2kg(2.65lb)Box content Camera,installation guide,TORX®L-keys,terminal blockconnector,connector guard,cable gaskets,AXIS Weather ShieldL,owner authentication keyOptionalaccessoriesAXIS T94F01M J-Box/Gang Box Plate,AXIS T91A47Pole Mount,AXIS T94P01B Corner Bracket,AXIS T94F01P Conduit Back Box,AXIS Weather Shield K,Axis PoE MidspansFor more accessories,go to /products/axis-p1465-le#accessoriesSystem tools AXIS Site Designer,AXIS Device Manager,product selector,accessory selector,lens calculatorAvailable at Languages English,German,French,Spanish,Italian,Russian,SimplifiedChinese,Japanese,Korean,Portuguese,Traditional Chinese Warranty5-year warranty,see /warrantyPart numbers Available at /products/axis-p1465-le#part-numbers SustainabilitySubstancecontrolPVC free,BFR/CFR free in accordance with JEDEC/ECA StandardJS709RoHS in accordance with EU RoHS Directive2011/65/EU/andEN63000:2018REACH in accordance with(EC)No1907/2006.For SCIP UUID,see /partner.Materials Screened for conflict minerals in accordance with OECDguidelinesTo read more about sustainability at Axis,go to/about-axis/sustainabilityEnvironmentalresponsibility/environmental-responsibilityAxis Communications is a signatory of the UN Global Compact,read more at a.We recommend a maximum of3unique video streams per camera or channel,for optimized user experience,network bandwidth,and storage utilization.A unique video stream can be served to many video clients in the network using multicast or unicast transport method via built-in stream reuse functionality.b.This product includes software developed by the OpenSSL Project for use in the OpenSSL Toolkit.(),and cryptographic software written by Eric Young (*****************).c.It also requires AXIS D2110-VE Security Radar with firmware10.12or later.Dimension drawingKey features and technologiesBuilt-in cybersecurityAxis Edge Vault is a secure cryptographic compute module (secure module or secure element)in which the Axis device ID is securely and permanently installed and stored. Secure boot is a boot process that consists of an unbro-ken chain of cryptographically validated software,starting in immutable memory(boot ROM).Being based on signed firmware,secure boot ensures that a device can boot only with authorized firmware.Secure boot guarantees that the Axis device is completely clean from possible malware after resetting to factory default.Signed firmware is implemented by the software vendor signing the firmware image with a private key,which is se-cret.When firmware has this signature attached to it,a device will validate the firmware before accepting and in-stalling it.If the device detects that the firmware integrity is compromised,it will reject the firmware upgrade.Axis signed firmware is based on the industry-accepted RSA pub-lic-key encryption method.ZipstreamThe Axis Zipstream technology preserves all the important forensic in the video stream while lowering bandwidth and storage requirements by an average of50%.Zipstream also includes three intelligent algorithms,which ensure that rel-evant forensic information is identified,recorded,and sent in full resolution and frame rate.Forensic WDRAxis cameras with wide dynamic range(WDR)technology make the difference between seeing important forensic de-tails clearly and seeing nothing but a blur in challenging light conditions.The difference between the darkest and the brightest spots can spell trouble for image usability and clarity.Forensic WDR effectively reduces visible noise and artifacts to deliver video tuned for maximal forensic usabil-ity.LightfinderThe Axis Lightfinder technology delivers high-resolution, full-color video with a minimum of motion blur even in near darkness.Because it strips away noise,Lightfinder makes dark areas in a scene visible and captures details in very low light.Cameras with Lightfinder discern color in low light better than the human eye.In surveillance,color may be the critical factor to identify a person,an object,or a vehicle.AXIS Object AnalyticsAXIS Object Analytics adds value to your camera for free.It detects and classifies humans,vehicles,and types of vehi-cles.Thanks to AI-based algorithms and behavioral con-ditions,it analyzes the scene and their spatial behavior within—all tailored to your specific needs.Scalable and edge-based,it requires minimum effort to set up and sup-ports various scenarios running simultaneously.Two lens alternativesThe camera is available in two variants with a choice of lenses:a wide3.9-9mm lens for wide area surveillance and a tele10-29mm lens for surveillance from a distance.OptimizedIRAxis OptimizedIR provides a unique and powerful combi-nation of camera intelligence and sophisticated LED tech-nology,resulting in our most advanced camera-integrated IR solutions for complete darkness.In our pan-tilt-zoom (PTZ)cameras with OptimizedIR,the IR beam automatically adapts and becomes wider or narrower as the camera zooms in and out to make sure that the entire field of view is al-ways evenly illuminated.For more information,see /glossary©2022-2023Axis Communications AB.AXIS COMMUNICATIONS,AXIS,ARTPEC and VAPIX are registered trademarks ofAxis AB in various jurisdictions.All other trademarks are the property of their respective owners.We reserve the right tointroduce modifications without notice.T10181832/EN/M13.2/2302。

Question

•
• • • •
4、Describing the three microscope models of treating the interaction between matters and light. 5、What is the phonon? 6、 What is the exciton? 7、 What is the plasmon? 8、Give the physics essence of dispersion.
• 16、What is the intersubband transitions? please give the transition select rules. • 17、Give the physics model of artificial atoms. • 18、 Emission in solids is called luminescence. Please descript the luminescence mechanisms.
• 15、The use of quantum well structure in EL devices is their main commercial application. Please state the advantage of quantum well .
• A greater range of emission wavelength; • An enhancement of device efficiency.
Questions
1、Describing the Classification of optical processes. 2 How 2、How many phenomena appear in propagation. 3、What the difference is between condensed matter and atomic or molecular optical physics?

热红外传感史

History of infrared detectorsA.ROGALSKI*Institute of Applied Physics, Military University of Technology, 2 Kaliskiego Str.,00–908 Warsaw, PolandThis paper overviews the history of infrared detector materials starting with Herschel’s experiment with thermometer on February11th,1800.Infrared detectors are in general used to detect,image,and measure patterns of the thermal heat radia−tion which all objects emit.At the beginning,their development was connected with thermal detectors,such as ther−mocouples and bolometers,which are still used today and which are generally sensitive to all infrared wavelengths and op−erate at room temperature.The second kind of detectors,called the photon detectors,was mainly developed during the20th Century to improve sensitivity and response time.These detectors have been extensively developed since the1940’s.Lead sulphide(PbS)was the first practical IR detector with sensitivity to infrared wavelengths up to~3μm.After World War II infrared detector technology development was and continues to be primarily driven by military applications.Discovery of variable band gap HgCdTe ternary alloy by Lawson and co−workers in1959opened a new area in IR detector technology and has provided an unprecedented degree of freedom in infrared detector design.Many of these advances were transferred to IR astronomy from Departments of Defence ter on civilian applications of infrared technology are frequently called“dual−use technology applications.”One should point out the growing utilisation of IR technologies in the civilian sphere based on the use of new materials and technologies,as well as the noticeable price decrease in these high cost tech−nologies.In the last four decades different types of detectors are combined with electronic readouts to make detector focal plane arrays(FPAs).Development in FPA technology has revolutionized infrared imaging.Progress in integrated circuit design and fabrication techniques has resulted in continued rapid growth in the size and performance of these solid state arrays.Keywords:thermal and photon detectors, lead salt detectors, HgCdTe detectors, microbolometers, focal plane arrays.Contents1.Introduction2.Historical perspective3.Classification of infrared detectors3.1.Photon detectors3.2.Thermal detectors4.Post−War activity5.HgCdTe era6.Alternative material systems6.1.InSb and InGaAs6.2.GaAs/AlGaAs quantum well superlattices6.3.InAs/GaInSb strained layer superlattices6.4.Hg−based alternatives to HgCdTe7.New revolution in thermal detectors8.Focal plane arrays – revolution in imaging systems8.1.Cooled FPAs8.2.Uncooled FPAs8.3.Readiness level of LWIR detector technologies9.SummaryReferences 1.IntroductionLooking back over the past1000years we notice that infra−red radiation(IR)itself was unknown until212years ago when Herschel’s experiment with thermometer and prism was first reported.Frederick William Herschel(1738–1822) was born in Hanover,Germany but emigrated to Britain at age19,where he became well known as both a musician and an astronomer.Herschel became most famous for the discovery of Uranus in1781(the first new planet found since antiquity)in addition to two of its major moons,Tita−nia and Oberon.He also discovered two moons of Saturn and infrared radiation.Herschel is also known for the twenty−four symphonies that he composed.W.Herschel made another milestone discovery–discov−ery of infrared light on February11th,1800.He studied the spectrum of sunlight with a prism[see Fig.1in Ref.1],mea−suring temperature of each colour.The detector consisted of liquid in a glass thermometer with a specially blackened bulb to absorb radiation.Herschel built a crude monochromator that used a thermometer as a detector,so that he could mea−sure the distribution of energy in sunlight and found that the highest temperature was just beyond the red,what we now call the infrared(‘below the red’,from the Latin‘infra’–be−OPTO−ELECTRONICS REVIEW20(3),279–308DOI: 10.2478/s11772−012−0037−7*e−mail: rogan@.pllow)–see Fig.1(b)[2].In April 1800he reported it to the Royal Society as dark heat (Ref.1,pp.288–290):Here the thermometer No.1rose 7degrees,in 10minu−tes,by an exposure to the full red coloured rays.I drew back the stand,till the centre of the ball of No.1was just at the vanishing of the red colour,so that half its ball was within,and half without,the visible rays of theAnd here the thermometerin 16minutes,degrees,when its centre was inch out of the raysof the sun.as had a rising of 9de−grees,and here the difference is almost too trifling to suppose,that latter situation of the thermometer was much beyond the maximum of the heating power;while,at the same time,the experiment sufficiently indi−cates,that the place inquired after need not be looked for at a greater distance.Making further experiments on what Herschel called the ‘calorific rays’that existed beyond the red part of the spec−trum,he found that they were reflected,refracted,absorbed and transmitted just like visible light [1,3,4].The early history of IR was reviewed about 50years ago in three well−known monographs [5–7].Many historical information can be also found in four papers published by Barr [3,4,8,9]and in more recently published monograph [10].Table 1summarises the historical development of infrared physics and technology [11,12].2.Historical perspectiveFor thirty years following Herschel’s discovery,very little progress was made beyond establishing that the infrared ra−diation obeyed the simplest laws of optics.Slow progress inthe study of infrared was caused by the lack of sensitive and accurate detectors –the experimenters were handicapped by the ordinary thermometer.However,towards the second de−cade of the 19th century,Thomas Johann Seebeck began to examine the junction behaviour of electrically conductive materials.In 1821he discovered that a small electric current will flow in a closed circuit of two dissimilar metallic con−ductors,when their junctions are kept at different tempera−tures [13].During that time,most physicists thought that ra−diant heat and light were different phenomena,and the dis−covery of Seebeck indirectly contributed to a revival of the debate on the nature of heat.Due to small output vol−tage of Seebeck’s junctions,some μV/K,the measurement of very small temperature differences were prevented.In 1829L.Nobili made the first thermocouple and improved electrical thermometer based on the thermoelectric effect discovered by Seebeck in 1826.Four years later,M.Melloni introduced the idea of connecting several bismuth−copper thermocouples in series,generating a higher and,therefore,measurable output voltage.It was at least 40times more sensitive than the best thermometer available and could de−tect the heat from a person at a distance of 30ft [8].The out−put voltage of such a thermopile structure linearly increases with the number of connected thermocouples.An example of thermopile’s prototype invented by Nobili is shown in Fig.2(a).It consists of twelve large bismuth and antimony elements.The elements were placed upright in a brass ring secured to an adjustable support,and were screened by a wooden disk with a 15−mm central aperture.Incomplete version of the Nobili−Melloni thermopile originally fitted with the brass cone−shaped tubes to collect ra−diant heat is shown in Fig.2(b).This instrument was much more sensi−tive than the thermometers previously used and became the most widely used detector of IR radiation for the next half century.The third member of the trio,Langley’s bolometer appea−red in 1880[7].Samuel Pierpont Langley (1834–1906)used two thin ribbons of platinum foil connected so as to form two arms of a Wheatstone bridge (see Fig.3)[15].This instrument enabled him to study solar irradiance far into its infrared region and to measure theintensityof solar radia−tion at various wavelengths [9,16,17].The bolometer’s sen−History of infrared detectorsFig.1.Herschel’s first experiment:A,B –the small stand,1,2,3–the thermometers upon it,C,D –the prism at the window,E –the spec−trum thrown upon the table,so as to bring the last quarter of an inch of the read colour upon the stand (after Ref.1).InsideSir FrederickWilliam Herschel (1738–1822)measures infrared light from the sun– artist’s impression (after Ref. 2).Fig.2.The Nobili−Meloni thermopiles:(a)thermopile’s prototype invented by Nobili (ca.1829),(b)incomplete version of the Nobili−−Melloni thermopile (ca.1831).Museo Galileo –Institute and Museum of the History of Science,Piazza dei Giudici 1,50122Florence, Italy (after Ref. 14).Table 1. Milestones in the development of infrared physics and technology (up−dated after Refs. 11 and 12)Year Event1800Discovery of the existence of thermal radiation in the invisible beyond the red by W. HERSCHEL1821Discovery of the thermoelectric effects using an antimony−copper pair by T.J. SEEBECK1830Thermal element for thermal radiation measurement by L. NOBILI1833Thermopile consisting of 10 in−line Sb−Bi thermal pairs by L. NOBILI and M. MELLONI1834Discovery of the PELTIER effect on a current−fed pair of two different conductors by J.C. PELTIER1835Formulation of the hypothesis that light and electromagnetic radiation are of the same nature by A.M. AMPERE1839Solar absorption spectrum of the atmosphere and the role of water vapour by M. MELLONI1840Discovery of the three atmospheric windows by J. HERSCHEL (son of W. HERSCHEL)1857Harmonization of the three thermoelectric effects (SEEBECK, PELTIER, THOMSON) by W. THOMSON (Lord KELVIN)1859Relationship between absorption and emission by G. KIRCHHOFF1864Theory of electromagnetic radiation by J.C. MAXWELL1873Discovery of photoconductive effect in selenium by W. SMITH1876Discovery of photovoltaic effect in selenium (photopiles) by W.G. ADAMS and A.E. DAY1879Empirical relationship between radiation intensity and temperature of a blackbody by J. STEFAN1880Study of absorption characteristics of the atmosphere through a Pt bolometer resistance by S.P. LANGLEY1883Study of transmission characteristics of IR−transparent materials by M. MELLONI1884Thermodynamic derivation of the STEFAN law by L. BOLTZMANN1887Observation of photoelectric effect in the ultraviolet by H. HERTZ1890J. ELSTER and H. GEITEL constructed a photoemissive detector consisted of an alkali−metal cathode1894, 1900Derivation of the wavelength relation of blackbody radiation by J.W. RAYEIGH and W. WIEN1900Discovery of quantum properties of light by M. PLANCK1903Temperature measurements of stars and planets using IR radiometry and spectrometry by W.W. COBLENTZ1905 A. EINSTEIN established the theory of photoelectricity1911R. ROSLING made the first television image tube on the principle of cathode ray tubes constructed by F. Braun in 18971914Application of bolometers for the remote exploration of people and aircrafts ( a man at 200 m and a plane at 1000 m)1917T.W. CASE developed the first infrared photoconductor from substance composed of thallium and sulphur1923W. SCHOTTKY established the theory of dry rectifiers1925V.K. ZWORYKIN made a television image tube (kinescope) then between 1925 and 1933, the first electronic camera with the aid of converter tube (iconoscope)1928Proposal of the idea of the electro−optical converter (including the multistage one) by G. HOLST, J.H. DE BOER, M.C. TEVES, and C.F. VEENEMANS1929L.R. KOHLER made a converter tube with a photocathode (Ag/O/Cs) sensitive in the near infrared1930IR direction finders based on PbS quantum detectors in the wavelength range 1.5–3.0 μm for military applications (GUDDEN, GÖRLICH and KUTSCHER), increased range in World War II to 30 km for ships and 7 km for tanks (3–5 μm)1934First IR image converter1939Development of the first IR display unit in the United States (Sniperscope, Snooperscope)1941R.S. OHL observed the photovoltaic effect shown by a p−n junction in a silicon1942G. EASTMAN (Kodak) offered the first film sensitive to the infrared1947Pneumatically acting, high−detectivity radiation detector by M.J.E. GOLAY1954First imaging cameras based on thermopiles (exposure time of 20 min per image) and on bolometers (4 min)1955Mass production start of IR seeker heads for IR guided rockets in the US (PbS and PbTe detectors, later InSb detectors for Sidewinder rockets)1957Discovery of HgCdTe ternary alloy as infrared detector material by W.D. LAWSON, S. NELSON, and A.S. YOUNG1961Discovery of extrinsic Ge:Hg and its application (linear array) in the first LWIR FLIR systems1965Mass production start of IR cameras for civil applications in Sweden (single−element sensors with optomechanical scanner: AGA Thermografiesystem 660)1970Discovery of charge−couple device (CCD) by W.S. BOYLE and G.E. SMITH1970Production start of IR sensor arrays (monolithic Si−arrays: R.A. SOREF 1968; IR−CCD: 1970; SCHOTTKY diode arrays: F.D.SHEPHERD and A.C. YANG 1973; IR−CMOS: 1980; SPRITE: T. ELIOTT 1981)1975Lunch of national programmes for making spatially high resolution observation systems in the infrared from multielement detectors integrated in a mini cooler (so−called first generation systems): common module (CM) in the United States, thermal imaging commonmodule (TICM) in Great Britain, syteme modulaire termique (SMT) in France1975First In bump hybrid infrared focal plane array1977Discovery of the broken−gap type−II InAs/GaSb superlattices by G.A. SAI−HALASZ, R. TSU, and L. ESAKI1980Development and production of second generation systems [cameras fitted with hybrid HgCdTe(InSb)/Si(readout) FPAs].First demonstration of two−colour back−to−back SWIR GaInAsP detector by J.C. CAMPBELL, A.G. DENTAI, T.P. LEE,and C.A. BURRUS1985Development and mass production of cameras fitted with Schottky diode FPAs (platinum silicide)1990Development and production of quantum well infrared photoconductor (QWIP) hybrid second generation systems1995Production start of IR cameras with uncooled FPAs (focal plane arrays; microbolometer−based and pyroelectric)2000Development and production of third generation infrared systemssitivity was much greater than that of contemporary thermo−piles which were little improved since their use by Melloni. Langley continued to develop his bolometer for the next20 years(400times more sensitive than his first efforts).His latest bolometer could detect the heat from a cow at a dis−tance of quarter of mile [9].From the above information results that at the beginning the development of the IR detectors was connected with ther−mal detectors.The first photon effect,photoconductive ef−fect,was discovered by Smith in1873when he experimented with selenium as an insulator for submarine cables[18].This discovery provided a fertile field of investigation for several decades,though most of the efforts were of doubtful quality. By1927,over1500articles and100patents were listed on photosensitive selenium[19].It should be mentioned that the literature of the early1900’s shows increasing interest in the application of infrared as solution to numerous problems[7].A special contribution of William Coblenz(1873–1962)to infrared radiometry and spectroscopy is marked by huge bib−liography containing hundreds of scientific publications, talks,and abstracts to his credit[20,21].In1915,W.Cob−lentz at the US National Bureau of Standards develops ther−mopile detectors,which he uses to measure the infrared radi−ation from110stars.However,the low sensitivity of early in−frared instruments prevented the detection of other near−IR sources.Work in infrared astronomy remained at a low level until breakthroughs in the development of new,sensitive infrared detectors were achieved in the late1950’s.The principle of photoemission was first demonstrated in1887when Hertz discovered that negatively charged par−ticles were emitted from a conductor if it was irradiated with ultraviolet[22].Further studies revealed that this effect could be produced with visible radiation using an alkali metal electrode [23].Rectifying properties of semiconductor−metal contact were discovered by Ferdinand Braun in1874[24],when he probed a naturally−occurring lead sulphide(galena)crystal with the point of a thin metal wire and noted that current flowed freely in one direction only.Next,Jagadis Chandra Bose demonstrated the use of galena−metal point contact to detect millimetre electromagnetic waves.In1901he filed a U.S patent for a point−contact semiconductor rectifier for detecting radio signals[25].This type of contact called cat’s whisker detector(sometimes also as crystal detector)played serious role in the initial phase of radio development.How−ever,this contact was not used in a radiation detector for the next several decades.Although crystal rectifiers allowed to fabricate simple radio sets,however,by the mid−1920s the predictable performance of vacuum−tubes replaced them in most radio applications.The period between World Wars I and II is marked by the development of photon detectors and image converters and by emergence of infrared spectroscopy as one of the key analytical techniques available to chemists.The image con−verter,developed on the eve of World War II,was of tre−mendous interest to the military because it enabled man to see in the dark.The first IR photoconductor was developed by Theodore W.Case in1917[26].He discovered that a substance com−posed of thallium and sulphur(Tl2S)exhibited photocon−ductivity.Supported by the US Army between1917and 1918,Case adapted these relatively unreliable detectors for use as sensors in an infrared signalling device[27].The pro−totype signalling system,consisting of a60−inch diameter searchlight as the source of radiation and a thallous sulphide detector at the focus of a24−inch diameter paraboloid mir−ror,sent messages18miles through what was described as ‘smoky atmosphere’in1917.However,instability of resis−tance in the presence of light or polarizing voltage,loss of responsivity due to over−exposure to light,high noise,slug−gish response and lack of reproducibility seemed to be inhe−rent weaknesses.Work was discontinued in1918;commu−nication by the detection of infrared radiation appeared dis−tinctly ter Case found that the addition of oxygen greatly enhanced the response [28].The idea of the electro−optical converter,including the multistage one,was proposed by Holst et al.in1928[29]. The first attempt to make the converter was not successful.A working tube consisted of a photocathode in close proxi−mity to a fluorescent screen was made by the authors in 1934 in Philips firm.In about1930,the appearance of the Cs−O−Ag photo−tube,with stable characteristics,to great extent discouraged further development of photoconductive cells until about 1940.The Cs−O−Ag photocathode(also called S−1)elabo−History of infrared detectorsFig.3.Longley’s bolometer(a)composed of two sets of thin plati−num strips(b),a Wheatstone bridge,a battery,and a galvanometer measuring electrical current (after Ref. 15 and 16).rated by Koller and Campbell[30]had a quantum efficiency two orders of magnitude above anything previously studied, and consequently a new era in photoemissive devices was inaugurated[31].In the same year,the Japanese scientists S. Asao and M.Suzuki reported a method for enhancing the sensitivity of silver in the S−1photocathode[32].Consisted of a layer of caesium on oxidized silver,S−1is sensitive with useful response in the near infrared,out to approxi−mately1.2μm,and the visible and ultraviolet region,down to0.3μm.Probably the most significant IR development in the United States during1930’s was the Radio Corporation of America(RCA)IR image tube.During World War II, near−IR(NIR)cathodes were coupled to visible phosphors to provide a NIR image converter.With the establishment of the National Defence Research Committee,the develop−ment of this tube was accelerated.In1942,the tube went into production as the RCA1P25image converter(see Fig.4).This was one of the tubes used during World War II as a part of the”Snooperscope”and”Sniperscope,”which were used for night observation with infrared sources of illumination.Since then various photocathodes have been developed including bialkali photocathodes for the visible region,multialkali photocathodes with high sensitivity ex−tending to the infrared region and alkali halide photocatho−des intended for ultraviolet detection.The early concepts of image intensification were not basically different from those today.However,the early devices suffered from two major deficiencies:poor photo−cathodes and poor ter development of both cathode and coupling technologies changed the image in−tensifier into much more useful device.The concept of image intensification by cascading stages was suggested independently by number of workers.In Great Britain,the work was directed toward proximity focused tubes,while in the United State and in Germany–to electrostatically focused tubes.A history of night vision imaging devices is given by Biberman and Sendall in monograph Electro−Opti−cal Imaging:System Performance and Modelling,SPIE Press,2000[10].The Biberman’s monograph describes the basic trends of infrared optoelectronics development in the USA,Great Britain,France,and Germany.Seven years later Ponomarenko and Filachev completed this monograph writ−ing the book Infrared Techniques and Electro−Optics in Russia:A History1946−2006,SPIE Press,about achieve−ments of IR techniques and electrooptics in the former USSR and Russia [33].In the early1930’s,interest in improved detectors began in Germany[27,34,35].In1933,Edgar W.Kutzscher at the University of Berlin,discovered that lead sulphide(from natural galena found in Sardinia)was photoconductive and had response to about3μm.B.Gudden at the University of Prague used evaporation techniques to develop sensitive PbS films.Work directed by Kutzscher,initially at the Uni−versity of Berlin and later at the Electroacustic Company in Kiel,dealt primarily with the chemical deposition approach to film formation.This work ultimately lead to the fabrica−tion of the most sensitive German detectors.These works were,of course,done under great secrecy and the results were not generally known until after1945.Lead sulphide photoconductors were brought to the manufacturing stage of development in Germany in about1943.Lead sulphide was the first practical infrared detector deployed in a variety of applications during the war.The most notable was the Kiel IV,an airborne IR system that had excellent range and which was produced at Carl Zeiss in Jena under the direction of Werner K. Weihe [6].In1941,Robert J.Cashman improved the technology of thallous sulphide detectors,which led to successful produc−tion[36,37].Cashman,after success with thallous sulphide detectors,concentrated his efforts on lead sulphide detec−tors,which were first produced in the United States at Northwestern University in1944.After World War II Cash−man found that other semiconductors of the lead salt family (PbSe and PbTe)showed promise as infrared detectors[38]. The early detector cells manufactured by Cashman are shown in Fig. 5.Fig.4.The original1P25image converter tube developed by the RCA(a).This device measures115×38mm overall and has7pins.It opera−tion is indicated by the schematic drawing (b).After1945,the wide−ranging German trajectory of research was essentially the direction continued in the USA, Great Britain and Soviet Union under military sponsorship after the war[27,39].Kutzscher’s facilities were captured by the Russians,thus providing the basis for early Soviet detector development.From1946,detector technology was rapidly disseminated to firms such as Mullard Ltd.in Southampton,UK,as part of war reparations,and some−times was accompanied by the valuable tacit knowledge of technical experts.E.W.Kutzscher,for example,was flown to Britain from Kiel after the war,and subsequently had an important influence on American developments when he joined Lockheed Aircraft Co.in Burbank,California as a research scientist.Although the fabrication methods developed for lead salt photoconductors was usually not completely under−stood,their properties are well established and reproducibi−lity could only be achieved after following well−tried reci−pes.Unlike most other semiconductor IR detectors,lead salt photoconductive materials are used in the form of polycrys−talline films approximately1μm thick and with individual crystallites ranging in size from approximately0.1–1.0μm. They are usually prepared by chemical deposition using empirical recipes,which generally yields better uniformity of response and more stable results than the evaporative methods.In order to obtain high−performance detectors, lead chalcogenide films need to be sensitized by oxidation. The oxidation may be carried out by using additives in the deposition bath,by post−deposition heat treatment in the presence of oxygen,or by chemical oxidation of the film. The effect of the oxidant is to introduce sensitizing centres and additional states into the bandgap and thereby increase the lifetime of the photoexcited holes in the p−type material.3.Classification of infrared detectorsObserving a history of the development of the IR detector technology after World War II,many materials have been investigated.A simple theorem,after Norton[40],can be stated:”All physical phenomena in the range of about0.1–1 eV will be proposed for IR detectors”.Among these effects are:thermoelectric power(thermocouples),change in elec−trical conductivity(bolometers),gas expansion(Golay cell), pyroelectricity(pyroelectric detectors),photon drag,Jose−phson effect(Josephson junctions,SQUIDs),internal emis−sion(PtSi Schottky barriers),fundamental absorption(in−trinsic photodetectors),impurity absorption(extrinsic pho−todetectors),low dimensional solids[superlattice(SL), quantum well(QW)and quantum dot(QD)detectors], different type of phase transitions, etc.Figure6gives approximate dates of significant develop−ment efforts for the materials mentioned.The years during World War II saw the origins of modern IR detector tech−nology.Recent success in applying infrared technology to remote sensing problems has been made possible by the successful development of high−performance infrared de−tectors over the last six decades.Photon IR technology com−bined with semiconductor material science,photolithogra−phy technology developed for integrated circuits,and the impetus of Cold War military preparedness have propelled extraordinary advances in IR capabilities within a short time period during the last century [41].The majority of optical detectors can be classified in two broad categories:photon detectors(also called quantum detectors) and thermal detectors.3.1.Photon detectorsIn photon detectors the radiation is absorbed within the material by interaction with electrons either bound to lattice atoms or to impurity atoms or with free electrons.The observed electrical output signal results from the changed electronic energy distribution.The photon detectors show a selective wavelength dependence of response per unit incident radiation power(see Fig.8).They exhibit both a good signal−to−noise performance and a very fast res−ponse.But to achieve this,the photon IR detectors require cryogenic cooling.This is necessary to prevent the thermalHistory of infrared detectorsFig.5.Cashman’s detector cells:(a)Tl2S cell(ca.1943):a grid of two intermeshing comb−line sets of conducting paths were first pro−vided and next the T2S was evaporated over the grid structure;(b) PbS cell(ca.1945)the PbS layer was evaporated on the wall of the tube on which electrical leads had been drawn with aquadag(afterRef. 38).。

光学效应英语作文

光学效应英语作文In the realm of physics, optical phenomena are thecaptivating interactions between light and matter that shape our visual experiences. These phenomena are not only fundamental to our understanding of the world but also play a crucial role in various technologies and applications we encounter daily.Reflection and Refraction: The most common optical effects are reflection and refraction. Reflection occurs when light bounces off a surface, as seen in mirrors that create images. Refraction, on the other hand, happens when light passes through a medium with a different density, causing it to change direction. This is the principle behind lenses used in eyeglasses and cameras.Dispersion: Dispersion is the separation of light into its constituent colors when it passes through a prism. Thiseffect is responsible for the beautiful rainbows we see after a rain shower, as sunlight is refracted and dispersed by raindrops.Diffraction: Diffraction is the bending of light around obstacles or through slits. It is the reason why we can see shadows with sharp edges and why light can spread out to illuminate areas behind an object, even though the object blocks a direct line of sight.Polarization: Polarization is the alignment of light waves in a specific direction. It is used in sunglasses to reduce glare from reflective surfaces like water or glass, making it easier to see in bright conditions.Total Internal Reflection: This occurs when light traveling from a denser medium to a less dense medium hits the boundary at an angle greater than the critical angle. Instead of passing through, the light is completely reflected back into the denser medium. This is the principle behind fiber optics, which is used for high-speed data transmission.Lenses and Optical Instruments: Lenses are the heart of many optical devices, from microscopes to telescopes. They use refraction to magnify, focus, or disperse light, allowing us to see objects at different scales and distances.Laser Technology: Lasers, which produce highly concentrated beams of light, are a product of optical phenomena. They have a wide range of applications, from medical procedures to industrial manufacturing and even in everyday items likelaser pointers.Optical Illusions: Optical illusions exploit the way our eyes and brain process visual information, often playing with perspective, contrast, and color to create images that trick our senses.Conclusion: Optical phenomena are not just scientific curiosities; they are integral to our daily lives. From the way we see the world around us to the technologies thatenhance our experiences, the study of light and its interactions with matter is a fascinating field that continues to inspire innovation and discovery.。

重庆市巴蜀中学2023-2024学年高二上学期期中英语试卷

高2025届高二(上) 半期考试英语试卷(命题人: 徐薇、孙小涵审题人: 杨静)注意事项:1. 答题前, 考生务必将自己的姓名、准考证号、班级、学校在答题卡上填写清楚。

2. 每小题选出答案后, 用2B铅笔把答题卡上对应题目的答案标号涂黑, 如需改动, 用橡皮擦干净后, 再选涂其他答案标号。

在试卷上作答无效。

3. 考试结束后, 请将答题卡交回, 试卷自行保存。

满分150分, 考试用时120分钟。

第I卷(选择题)第一部分听力(共两节, 满分20分)第一节(共5小题: 每小题1分, 满分5分)听下面5段对话。

每段对话后有一个小题, 从题中所给的A、B、C三个选项中选出最佳选项。

听完每段对话后, 你都有10秒钟的时间来回答有关小题和阅读下一小题。

每段对话仅读一遍。

1. What’s wrong with the woman’s foot?A. It’s broken.B. It has a skin disease.C. It got burned by hot oil.2. What was Sparky probably doing?A. Trying on a hat.B. Destroying a hat or a tie.C. Chewing on one of his toys.3. Where does the woman want to go?A. To the office.B. To the library.C. To the dining hall.4. Why did the woman start her business?A. To learn about dogs.B. To help her neighbors.C. To finish a research project for school.5. Where might the speakers be?A. On a bridge.B. At a movie theater.C. In a car.第二节(共15小题: 每小题1分, 满分15分)听下面5 段对话或独白。

太空镜子的利弊英语作文

太空镜子的利弊英语作文Title: The Pros and Cons of Space Mirrors。

Introduction:Space mirrors, also known as sunshields or sunshades, are a proposed technology aimed at mitigating the effects of global warming by reflecting a portion of the sun's rays away from Earth. While this concept holds promise, it also raises several considerations regarding its potential benefits and drawbacks.Pros:1. Climate Mitigation:Space mirrors have the potential to reduce the amount of solar radiation reaching Earth's surface, thereby mitigating the impacts of global warming. By reflecting sunlight away from the planet, they could help regulatetemperatures and alleviate some of the adverse effects of climate change.2. Versatility:Space mirrors offer a versatile solution to address climate issues. Unlike certain geoengineering techniques that involve large-scale interventions on Earth's surface, space mirrors operate from outer space, allowing for more precise control and adjustment of the reflected sunlight.3. Global Impact:Implementing space mirrors could have a global impact on climate regulation. Since they operate on a planetary scale, their effects could be distributed evenly across different regions, potentially benefiting populations worldwide.4. Reversibility:One advantage of space mirrors is theirreversibility. Unlike some geoengineering approaches, which may have irreversible consequences or unintended side effects, space mirrors could be adjusted or removed relatively easily if necessary, providing a degree of flexibility in managing climate interventions.Cons:1. Cost:One of the primary concerns surrounding space mirrors is the high cost associated with their deployment and maintenance. Launching objects into space requires significant financial resources, and maintaining a network of mirrors in orbit would incur ongoing expenses.2. Technological Challenges:Developing and deploying space mirrors present significant technological challenges. Designing lightweight yet durable mirrors capable of withstanding the harsh conditions of space, as well as establishing reliabledeployment and positioning mechanisms, would require substantial research and innovation.3. Environmental Risks:Introducing space mirrors into Earth's orbit carries inherent environmental risks. Potential hazards include collisions with space debris, which could damage the mirrors and create additional debris, further exacerbating the problem of space junk.4. Ethical Considerations:The deployment of space mirrors raises ethical questions regarding humanity's role in altering the Earth's natural systems. Critics argue that relying on technological interventions to address climate change may divert attention and resources away from more sustainable solutions, such as reducing greenhouse gas emissions and promoting renewable energy.Conclusion:Space mirrors represent a novel approach to mitigating the effects of global warming, offering potential benefits such as climate regulation on a global scale and reversibility. However, their deployment entailssignificant challenges and risks, including high costs, technological hurdles, environmental concerns, and ethical considerations. As such, careful evaluation anddeliberation are necessary before considering the widespread implementation of space mirrors as a solution to climate change.。

The properties of optical coatings

The properties of optical coatingsOptical coatings have become an indispensable component in a wide range of modern technological applications. From high-performance camera lenses to cellphone screens, optical coatings play a crucial role in determining the quality and efficiency of the device. In this article, we will explore the different properties of optical coatings, and how they affect the overall performance of optical devices.Optical coatings are thin layers of material that are deposited onto a substrate. These coatings are designed to modify the optical properties of the substrate, such as its reflectivity, transmissivity, and absorption properties. Some common examples of optical coatings include anti-reflective coatings, reflective coatings, and filters.Perhaps the most important property of optical coatings is their spectral response. This refers to the way in which the coating interacts with light at different wavelengths. For example, an anti-reflective coating is designed to minimize the reflection of light across a wide range of wavelengths, while a filter is designed to allow only specific wavelengths to pass through.Another important property of optical coatings is their thickness and uniformity. The thickness of an optical coating can have a significant impact on its optical properties. If the coating is too thin or too thick, it may not effectively modify the optical properties of the substrate. Additionally, if the coating is not uniform across the surface of the substrate, it may cause unwanted optical effects.The durability and adhesion of optical coatings are also important properties to consider. Optical coatings are often subjected to a range of environmental factors, such as temperature changes, humidity, and exposure to chemicals. A coating that is not durable may degrade over time, impacting the optical performance of the device. Similarly, a coating that does not adhere well to the substrate may peel or flake off, also impacting the device's performance.Optical coatings can also be designed to exhibit certain mechanical properties, such as scratch resistance and hardness. These properties can be important in applications where the device will be subjected to physical wear and tear, such as eyeglasses. A coating that is too soft may be easily scratched, reducing its optical performance and overall lifespan.Finally, the optical properties of coatings can be affected by the manufacturing process used to produce them. Different deposition methods, such as sputtering or thermal evaporation, can result in coatings with varying properties. Additionally, the type of material used to produce the coating can impact its optical performance.In conclusion, optical coatings play a critical role in determining the optical properties of a wide range of devices. The spectral response, thickness and uniformity, durability and adhesion, mechanical properties, and manufacturing method are all important properties to consider when designing and selecting optical coatings. By understanding these properties, we can create more efficient, durable, and high-performance optical devices.。

光学效应英语作文

光学效应英语作文1. The optical effect of a rainbow is truly mesmerizing, with its vibrant colors stretching across the sky in a beautiful arc.2. When light passes through a prism, it is refracted and dispersed into its component colors, creating astunning display of the visible spectrum.3. The phenomenon of total internal reflection occurs when light travels from a medium with a higher refractive index to one with a lower refractive index, causing thelight to reflect back into the original medium.4. Mirages are another fascinating optical effect,where hot air near the ground causes light to bend and create illusions of water or objects that are not actually there.5. Diffraction is a phenomenon where light waves bendaround obstacles, creating patterns of light and dark fringes that can be observed in everyday life, such as when light passes through a narrow slit.6. The concept of polarization involves aligning light waves in a specific orientation, which can be seen in polarized sunglasses that reduce glare and improvevisibility in bright conditions.7. Holography is a unique optical effect that uses interference patterns to create three-dimensional images, adding depth and realism to photographs and other visual media.8. The optical effect of fluorescence occurs when a substance absorbs light at one wavelength and emits light at a longer wavelength, producing a glowing or fluorescent appearance.。

用科学解决近视的600字英语作文

用科学解决近视的600字英语作文Overcoming Myopia: A Scientific Approach.Myopia, commonly known as nearsightedness, has become a global epidemic, affecting billions of people worldwide. This condition makes it difficult to see distant objects clearly while objects close to the eye appear sharp. While corrective lenses and surgeries have been the traditional remedies, scientific research offers promising alternative approaches to tackling myopia and restoring clear vision.Understanding Myopia: The Root Cause.Myopia occurs when the eyeball is too long or thecornea (the clear outer layer of the eye) is too curved. This causes light to focus in front of the retina, thelight-sensitive tissue at the back of the eye. Consequently, the brain receives blurry images of distant objects.The Science of Myopia Control.Over the past decade, researchers have made significant strides in understanding the development of myopia. They have identified key factors that contribute to myopia progression and developed innovative strategies to slow or even halt its advancement.Orthokeratology (Ortho-K): Reshaping the Cornea.Ortho-k involves wearing specially designed rigid contact lenses during the night. These lenses gently reshape the cornea, temporarily flattening it and reducing its curvature. By changing the way light enters the eye, ortho-k improves distance vision. The effects typicallylast throughout the day, allowing the wearer to see clearly without glasses or contact lenses during the day.Atropine Eye Drops: Blocking Growth Signals.Atropine is a medication that has been shown to reduce myopia progression in children. It works by blockingcertain neurotransmitters that stimulate the elongation ofthe eyeball. By inhibiting this growth signal, atropine effectively slows down or even stops the worsening of myopia.Multifocal Contact Lenses: Reducing Blur.Multifocal contact lenses contain multiple prescriptions that gradually change in power from the center to the periphery of the lens. By presenting a clear image at all distances, these lenses reduce the strain on the eye, making it less likely to adapt and become more nearsighted.Behavioral Modifications: Preventing Myopia.In addition to these optical and pharmacological interventions, behavioral changes can also play a crucial role in myopia control. Spending more time outdoors, reducing screen time, and maintaining proper posture have all been linked to a lower risk of myopia development.Research and Future Directions.Scientific research is continuously advancing our understanding of myopia and its potential treatments. Ongoing studies are investigating the effects ofnutritional supplements, genetic factors, and environmental influences on myopia progression. By combining scientific evidence, technological innovations, and behavioral modifications, we are moving closer to a future where myopia is no longer an obstacle to clear vision.Conclusion.The scientific approach to myopia provides a comprehensive understanding of the condition and offers effective strategies for its control. By embracing advancements in optical technology, pharmacological interventions, and behavioral modifications, we can empower individuals to overcome myopia and achieve optimal visual clarity.。

浅水效应英语

浅水效应英语The Shallow Water EffectThe shallow water effect, also known as the shallows effect, is a fascinating phenomenon that occurs in various bodies of water, from lakes and rivers to coastal areas. This effect is characterized by the distortion of light and the perception of depth, creating an optical illusion that can captivate observers.At its core, the shallow water effect is a result of the interaction between light and the water's surface. When light travels from the air into the water, it bends or refracts due to the difference in the speed of light in these two mediums. This refraction causes objects beneath the water's surface to appear closer or farther away than they actually are, depending on the depth and other environmental factors.One of the most striking manifestations of the shallow water effect is the apparent reduction in depth. Shallow bodies of water often appear much shallower than they truly are, making it seem as if the bottom is closer to the surface than it actually is. This illusion can be particularly pronounced in clear, calm waters, where the lack ofturbulence and the high visibility allow for a more pronounced distortion of depth perception.Another notable aspect of the shallow water effect is the way it can alter the appearance of objects beneath the water's surface. Submerged objects may appear to be distorted, elongated, or even duplicated, creating a sense of visual disorientation. This effect is particularly noticeable when observing objects such as rocks, logs, or even fish, as they seem to shift and change shape as the light interacts with the water's surface.The shallow water effect is not limited to the perception of depth and object distortion; it can also influence the way colors are perceived. The water's surface can act as a filter, absorbing and scattering certain wavelengths of light, resulting in a shift in the perceived hues of underwater objects. This color distortion can be particularly striking in areas with clear, shallow waters, where the light penetration is high and the water's influence on the color spectrum is more pronounced.The shallow water effect has captured the attention of artists, photographers, and scientists alike, who have sought to understand and capture its unique visual qualities. Photographers, for example, often use the shallow water effect to create striking and otherworldly images, playing with the distortion of depth and the interplay of lightand water to produce captivating compositions.In the realm of science, the shallow water effect has been the subject of extensive research and study. Oceanographers and limnologists (scientists who study inland bodies of water) have delved into the physics and optics behind this phenomenon, exploring the complex interplay of factors that contribute to its formation. These studies have not only helped to deepen our understanding of the natural world but have also led to practical applications, such as the development of underwater imaging and navigation technologies.One area where the shallow water effect has particular significance is in the field of marine biology and ecology. The distortion of depth and the altered perception of underwater objects can have important implications for the study and observation of aquatic organisms. Researchers must take the shallow water effect into account when conducting surveys, monitoring populations, and studying the behavior of marine life, as the visual cues they receive may not accurately reflect the true state of the environment.Moreover, the shallow water effect has broader implications for our understanding of the natural world and our perception of it. The way we interpret and interact with our surroundings is heavily influenced by the way our senses, particularly vision, process the information they receive. The shallow water effect serves as a reminder that ourperceptions can be shaped by the physical properties of the environment, and that our understanding of the world is often mediated by the limitations and biases of our sensory systems.In conclusion, the shallow water effect is a captivating and multifaceted phenomenon that has captured the attention of artists, scientists, and nature enthusiasts alike. From its impact on our visual perception to its practical applications in fields such as marine biology and oceanography, the shallow water effect continues to fascinate and challenge our understanding of the natural world. As we continue to explore and study this intriguing optical illusion, we may uncover new insights into the complex interplay between light, water, and our own sensory experiences.。

关于障眼法的英语作文

关于障眼法的英语作文The Art of Illusion: An Introduction to Optical Illusions。

Optical illusions, also known as visual illusions, are fascinating phenomena that can trick our brain into perceiving something that is not actually there or distorting our perception of reality. They are created by manipulating the visual cues that our eyes receive, such as color, light, shadow, and perspective. Optical illusions have been used for centuries in art, design, and entertainment to create stunning and mind-bending effects. In this essay, we will explore the art of illusion and some of the most famous optical illusions.One of the most famous optical illusions is theMüller-Lyer illusion, which was first discovered by the German psychologist Franz Müller-Lyer in 1889. This illusion consists of two lines of equal length with different arrowheads at the ends. One arrowhead is pointedinward, and the other is pointed outward. Even though the lines are the same length, our brain interprets the line with the outward-pointing arrowhead as longer than the line with the inward-pointing arrowhead. This illusion is so powerful that it can even fool people who are aware of the trick.Another popular optical illusion is the Ponzo illusion, which was first described by the Italian psychologist Mario Ponzo in 1911. This illusion consists of two identical horizontal lines that are placed between two converging lines that recede into the distance. Even though the two lines are the same length, our brain perceives the linethat is closer to the converging lines as longer than the line that is farther away. This illusion is based on the concept of linear perspective, which is a technique used in art to create the illusion of depth and three-dimensionality.The Ames room is another famous optical illusion that was invented by the American psychologist Adelbert Ames Jr. in 1946. This illusion consists of a room that is shapedlike a trapezoid and is viewed from a peephole. The room appears to be rectangular, but in reality, one corner is much closer to the viewer than the other corner. This creates the illusion that people who are standing in the room are either giant or dwarf, depending on their position in the room. The Ames room is often used in movies and TV shows to create the illusion of characters changing size.In conclusion, optical illusions are a fascinating aspect of human perception that have been used for centuries in art, design, and entertainment. They can trick our brain into perceiving something that is not actually there or distorting our perception of reality. Some of the most f amous optical illusions include the Müller-Lyer illusion, the Ponzo illusion, and the Ames room. By understanding the art of illusion, we can appreciate the power of our brain and the complexity of the world around us.。

INSIGHT Physics Trial Exam 2 Solutions Book - 2006

INSIGHTTrial Exam Paper2006PHYSICSWritten examination 2Worked SolutionsThis book presents:•worked solutions, giving you a series of points to show you how to work through the questions•mark allocation details.This trial examination produced by Insight Publications is NOT an official VCAA paper for the 2006 Physics writtenexamination 2.This examination paper is licensed to be printed, photocopied or placed on the school intranet and used only within theconfines of the purchasing school for examining their students. No trial examination or part thereof may be issued or passed onSECTION A – CoreAREA OF STUDY 1 – Electric PowerQuestions 1 to 3 refer to the following information.As part of a Year 12 Physics experiment the following apparatus (Figure 1), consisting of two coils, a 6 V battery, a switch S, and a 200 Ω resistor is assembled.WXCoil ACoil CFigure 1Coil A has a soft iron core inside of it. Nearby, coil C is wound around a thin plastic tube and has a sensitive galvanometer attached to it. Between the two coils a bar magnet is suspended as shown.Question 1When the switch S is first closed the magnetic field inside coil AA. is non-existent because the current is not AC.B. is in the direction from W to X.C. is in the direction from X to W.D. remainsunchanged.2 marks Answer is BWorked solutionUntil the switch is closed there is no magnetic field inside coil A due to the wire.There is a magnetic field due to the proximity of the bar magnet in the direction of X to W. Coil A will not produce an opposing field for two reasons. Firstly: the circuit is not complete so no current can flow, and no magnetic field due to current in the coil will be produced. Secondly: assume the circuit were closed, and that the coil could therefore conduct. Even if this were the case, a current would be induced in the coil only when the magnetic field inside it changed.Explain what effect closing switch S would have on the suspended bar magnet and coil C. Answer•The current flowing through coil A makes it act like an electromagnet with its north pole at X and its south pole at W.•This results in the bar magnet being repelled from end X of coil A, towards coil C.•As the bar magnet moves toward coil C it will increase the size of the magnetic field inside coil C.•Coil C will try to oppose the increase in flux through it and induce a current to produce an opposing flux.•The current will flow through the galvanometer in the direction from Z to Y (right to left).3 marks Mark allocation• 1 mark for stating that the bar magnet will be repelled• 1 mark for stating the increase of the magnetic field• 1 mark for stating that coil C will try to oppose the increase in flux.•Drawing on the diagram is also acceptable to show the direction of the current described in the third dot point.Question 3When switch S is closed the needle of the galvanometer attached to coil C willright.A. moveleft.B. moveC. move right then return to the neutral position.D. move left then return to the neutral position.move.E. not2 marks Answer is DWorked solutionCoil C will only induce a magnetic field while the field inside it is changing. As soon as the bar magnet stops moving, the induced magnetic field will cease. Thus the galvanometer will only register a current for a short duration.Tip•The right-hand grip rule is used to determine the direction of the induced current. You must always pay attention to the direction the coil is wound. In this case the magneticfield is getting stronger in the direction from Z to Y, therefore the induced current must produce a magnetic field in the direction from Y to Z. To do this, the current musttravel down the exposed turns of the coil, thus travelling through the galvanometer inthe direction from Z to Y (right to left).Sally and Ben are discussing the construction of a DC motor. Sally claims that they need to use a commutator, but Ben thinks that slip rings are the correct component to use. Who is correct and why?Answer•Sally is correct.•For each half cycle (or rotation) of the coil, the current through the coil must change direction to keep the coil rotating in the same direction.•DC current never changes direction by itself, so the commutator changes the direction of the current by changing which side of the coil is positive every 180o.3 marks Mark allocation• 1 mark for stating that Penny is correct• 1 mark for the change in direction of the current• 1 mark for the commutator changing direction every 180oTip•Slip rings cannot change which side of the coil they are attached to and so can only work if the supply voltage is changing (i.e. if the current is AC).Question 5Sally decides to build her design as shown below in Figure 2. Describe what happens when she closes the switch. Justify your answer.NFigure 2Answer•Nothing happens. The loop remains stationary.•The force (F) generated according to the right-h and slap rule will be out to the sides of the loop.These forces will not provide any torque (turning force) about the axis of rotation.•N3 marksMark allocation • 1 mark per lineIshmael’s train set is constructed on a large table in the centre of the room. His train set uses a transformer to convert the mains AC supply from 240 V RMS to 12 V RMS. Ishmael is tired of tripping over the extension lead running from the wall socket to the transformer so he decides to connect the transformer to the wall socket and run two long wires up the wall and across the roof to his train set. The wires are each 5 metres long and have a resistance of 0.001 Ω per metre. Question 6The primary coil of the transformer has 1800 turns. How many turns must the secondary coil possess in order to convert from 240 V RMS to 12 V RMS?Worked solution turns 90240121800180012240222121=×=⇒=⇒=N N N N V V 2 marksMark allocation• 1 mark for correct substitution into formula • 1 mark for correct answerIshmael finds that his trains are not moving as quickly as before. A possible reason for this is that A. the transformer is connected with the secondary coil attached to the mains supply. B. Ishmael has fewer trains than normal on the track at one time. C. the wires connecting the transformer to the train set are too short. D. the wires connecting the transformer to the train set are too long.2 marksAnswer is DWorked solutionThe trains are receiving less power than before due to power losses in the lines. The lowvoltage out of the transformer means the wires are carrying high current. Since P loss = I 2R, the longer the wires the greater the resistance, so the greater the power loss. This would not be as noticeable when only a short length of wire is used between the transformer and the train set.Question 8Ishmael measures the current out of the secondary coil of the transformer as being 100 A RMS. What is the power of the transformer? Worked solutionP = VI = 12 × 100 = 1200 W OrA 5201002020211221===⇒==I I I I N N ⇒ P = VI = 240 × 5 = 1200 W2 marksMark allocation• 2 marks for the correct answerFind the peak voltage across the secondary coil of the transformer at this time. Worked solutionV p rms V 1216.9717V === V rms = 12 V from original information2 marksMark allocation• 2 marks for the correct answerQuestion 10How much power is being lost in the wires? Worked solution P loss = I 2R lineR line = 2 × 5 × 0.001 = 0.01 Ω P loss = 1002 × 0.01 = 100 W3 marksMark allocation• 3 marks for correct answer• 2 marks if only 5 m of wire used (ie P loss is calculated as being 50 W). Tip• Make sure you read the question carefully to check whether the resistance is quoted as a figure per metre, or as one figure for the entire length of wire used.The orientation of the rectangular coil in an AC generator is compared with the flux passing through each turn of the coil. The coil has 100 turns. Figure 3 shows the coil orientation whilst Figure 4 shows the magnetic flux through the coil at the same point in time.t = 0 ms t = 4 ms t = 8 ms t = 12 ms t = 16 msFigure 3B Φ(Wb)Figure 4Question 11From the above information, calculate the average EMF generated. Worked solution31000.00250V 410B N t ε−−ΔΦ−×===−Δ×= 50 V (negative sign is not important) 3 marksMark allocation• 1 mark for using 100 turns• 1 mark for correct substitution into formula • 1 mark for correct answerOver the same time period, which graph best represents the induced EMF?2 marksAnswer is AWorked solutionThe EMF waveform can be determined by taking the negative gradient of the slope of the flux–time graph.AB CDDescribe how the above EMF waveform would change if the rotational speed of the coils was halved.AnswerPeriod would double.Maximum voltage would halve.V-V2 marksMark allocation• 1 mark for noting that the period would double• 1 mark for noting that the maximum voltage would have• If students choose to draw the diagram, full marks will be awarded.Question 14The dimensions of the coil are 40 cm × 20 cm. Find the size of the magnetic field inside the coil.Worked solution0.0020.025T 0.40.2B B BA B A ΦΦ=⇒===× 3 marksMark allocation• 1 mark for converting the area to m 2• 2 marks for the transformation of equation and correct answer Tip• Remember to convert the dimensions of the coils to metres to get answer in the right units.A small bar magnet is suspended by a spring above a solenoid as shown in Figure 5.Figure 5Use the following key to answer questions 15 to 17. (One or more answers may be given.)KEY:A. The needle experiences no change.B. The needle moves to the left.C. The needle moves to the right.D. The needle moves left then right.E. The needle moves right then left.F. The needle does not deflect.Initially the magnet is stationary.Question 15Use the above key to describe what happens to the needle of the galvanometer when the switch is first closed.2 marks Answers are A and FTip•Since the magnetic field has not changed inside the coil there will be no induced current.Mark Allocation• 2 marks for both correct answers• 1 mark for only 1 correct answer• 1 mark off for any incorrect answer given, down to 0 marks.Question 16The spring is now stretched slowly so that the magnet approaches the solenoid. During this time, what happens to the needle?2 marks Answer is CWorked solutionThe magnetic field (pointing downwards) will increase inside the coil; the coil will try to oppose this change by inducing a current which produces an upwards magnetic field. Using the right-hand grip rule, the current must travel in an anticlockwise direction in the coil, and so the needle deflects to the right.Question 17The spring is now released, and the magnet moves up and down repeatedly. Use one of the keys A to F to describe the motion of the needle during this time.2 marksWorked solutionAs the magnet moves, the magnetic field will vary inside the coil, increasing as the magnet nears the solenoid and decreasing as it moves away. The coil will induce its own field to oppose any change, and thus will produce an upwards magnetic field as the magnet nears the solenoid and a downwards one as it moves away. Hence, the needle will move back and forth, indicating the alternating direction of the current.Mark allocation• 2 marks for D or E or both•0 marks for any other answer.END OF AREA OF STUDY 1AREA OF STUDY 2 – Interactions of light and matterUse the following key to answers questions 1 and 2.Light sourceA. LaserB. Sodium vapour lampC. Incandescent light globeLEDD. BlueQuestion 1Which of the above light sources produces coherent light?Worked solutionOnly lasers produce wave trains of monochromatic photons at the same time. This is coherence.A sodium vapour lamp produces defined wavelengths of light, but the photons are not in phase.A blue LED produces a narrow range of wavelengths. An incandescent globe produces a wide spectrum of wavelengths.2 marks Question 2Which one or more of the above light sources produce photons of discrete wavelengths?2 marks Answers are A and BMark allocation• 1 mark for each correct answer, minus 1 mark down to 0 for each incorrect answer.Tip•Refer to question 1 for an explanation of light source properties.Andre is investigating the photoelectric effect by varying the frequency of light incident upon a sodium metal cathode. The apparatus is shown in Figure 1.Figure 1For each frequency, the stopping potential V s is recorded by Andre.Trial no. Frequency(× 1014 Hz)V s (V)1 3.0 0.02 4.0 0.03 5.00.04 6.0 0.25 7.0 0.56 8.0 1.17 9.0 1.4Question 3What is the maximum energy a photoelectron can possess as it leaves the cathode if the incident light used has a frequency of 9 × 1014 Hz?Worked solutionE max (photon) = qV sFrom the table: at 9 × 1014 Hz,V s = 1.4 V=1× 1.4= 1.4 eV ( = 2.24 × 10-19 J)2 marks Mark allocation• 1 mark per line of the equation•Full marks for correct answer in Joules if units are changed in the answer box.Plot Andre’s data on the axes provided and hence or otherwise justify the statement that the work function for sodium is 2.4 eV.AnswerGraph should appear as below:Line of best fit equation:3 marks Mark allocation• 1 mark for correctly plotted points• 1 mark for straight line graph extended to Y-axis• 1 mark for explanation that Y-intercept is equal to work function of metal in eVTip•Plot points carefully. Ignore the zero values when constructing the ‘line of best fit’. Zero values indicate only that there is no current flowing. This is because there is nophotoelectrons being ejected. Do not confuse the last zero reading with the cut-offfrequency – the cut-off frequency may fall below that the last zero reading. In this casefrom the graph you can see that the cut-off frequency is approximately 5.5 × 1014 Hz.The table is not accurate enough to do calculations from. It is only useful for plottingdata points.From your graph calculate Planck’s constant.radient is Planck’s constant h = ΔV /Δf ≈ 0.42 × 10–14 = 4.2 × 10–15 eVsdepending on line of best fit (accept answers from 3.4 × 10–15 up to3 marksMark allocation• 1 mark for selecting 2 points from the graph. They cannot be points from the table calculation. Working must be shown.An flowing through the ir t pring half of the lightWorked solutionG Answers will vary 5.0 × 10-15). . • 2 marks for • 0 marks if 4.14 × 10–15is written without any working shown.dre now fixes the frequency at 7 × 10 Hz, and records the current cui for various stopping otentials. He then plots his results to obtain the graph labelled X 14c below in Figure 2.XFigure 2Andre then repeated this experiment with a piece of thick cardboard cove source.VWhich one of the graphs A to E is most likely to indicate the results of this repeated experiment?2 marks Answer is BWorked solutionBy halving the light intensity the number of photons striking the cathode is halved therefore only half as many photoelectrons are released and the current is reduced. The photoelectrons will still have the same maximum kinetic energy because the energy of the photons used to release them is determined by the frequency of the photons, which is unchanged.Tip• A change in stopping potential is caused by a change in frequency. A change in current is caused by a change in intensity.A laser is used as the light source for a demonstration of Young’s ‘Double Slit’ experiment as shown in Figure 3.S1 and S2 are slits through which the laser light passes, and the dotted lines represent wave fronts. Boxes A to L are parallel sections of the screen onto which the light falls.Figure 3Shade in any of the boxes A to L which represent regions on the screen which will appear bright.AnswerCorrect answer is to shade in regions B, D, F, H, J, L.Red lines indicate maxima. These appear as bright bands on the screen. Bands should be equally spaced apart.3 marksMark allocation• 3 marks if all shading is correct• 2 marks if L is not shaded in but the rest are correctly shaded• 1 mark if only F is shaded and minus 1 mark for each wrong region shaded down to 0marksTwo students who observe the demonstration are discussing whether the same effect would be observed if the slits were removed and two identical lasers were used instead. Brad thinks the interference pattern will change. Amy thinks the pattern will not. Who is correct and why? Answer• Brad is correct• Even though the lasers are identical, each will not produce photons at exactly the sametime – this means that the light will not be in phase from both sources.• The interference pattern will not be seen, as constructive and destructive interference willnot occur.3 marksMark allocation• 1 mark for stating that Brad is correct • 1 mark per reasonAn electron in an excited energy level of a mercury atom emits a photon of wavelength 175 nm as it changes energy levels, as shown in Figure 4.Figure 4n = 2n = 3 –3.3 eV –-5.5 eV–10.4 eV E = 0 eV n = 1n = 4 – 1.6 eV Question 9What energy level was the electron in before it emitted the photon? Worked solution158photon94.14103107.1eV 17510hcE λ−−×××===× 10.4 – 7.1 = 3.3 (subtract photon energy from energy levels to find an answer that equals one ofthe levels given.)So electron was originally in the n = 3 energy level3 marksMark allocation• 1 mark for the equation • 1 mark for each lineTip• Use h = 4.14 × 10-15eVs if data is given in eV instead of 6.63 × 10 -34 JQuestion 10Which of the following wavelengths is not possible for an emitted photon from this atom?nmA. 565nmB. 318nmC. 253nmD. 226Answer is DWorked solutionUse λ = hc/ΔE to find wavelengths, where ΔE is the difference in energy levels.Answer A corresponds to the n3 to n2 transition; answer B to the n4 to n2 transition; and answer C to the n2 to n1 transition.Answer D corresponds to 5.5 eV, which is an energy level, rather than a difference between energy levels.2 marksSECTION B – Detailed StudiesDETAILED STUDY 1 – Synchrotron and its applicationsUse the diagram and key shown in Figure 1 to answer questions 1 to 3.Figure 1Question 1At which of the points A to F would a wiggler be found?2 marks Answer is BTips•Wigglers are only used in the storage ring of a synchrotron and are placed in the straight sections between bending magnets.Question 2Where are bending magnets located in the above diagram?2 marks Answers are A and CTip•Bending magnets are found in both the storage and booster rings.Mark allocation• 1 mark for each correct answer, minus 1 mark for each incorrect answer down to 0 marks.Indicate at which points from A to F radio frequency (RF) cavities could be located.2 marksAnswers are B and E. Tip• RF cavities are used in the electron gun to pulse the electrons produced and in thestorage ring to rebunch electrons.Mark allocation• 1 mark for each correct answer, minus 1 mark for each incorrect answer down to 0marksQuestion 4In a small synchrotron, it is planned to use bending magnets which produce a field strength of 0.5 T to contain the electron beam in a curve of radius 14 m. What momentum must the electrons possess to maintain this radius? Worked solutionBrq p qBp r =⇒=⇒ p = 0.5 × 14 × 1.6 × 10-19 = 1.12 × 10–18 kg m s –12 marksMark Allocation•.1 mark for correct substitution • 1 mark for the answerThe electrons are initially accelerated from 0 ms–1 by an electron gun. The potential difference across the plates of the electron gun is 6000 V. With what energy does each electron leave the electron gun? Give your answer in joules.Worked solutionE = Vq = 6000 × 1.6 × 10–19= 9.6 × 10–16 J2 marks Mark allocation• 1 mark for the answer• 1 mark for conversion to Joules•If answer given as 6000 eV only 1 mark will be awardedQuestion 6Explain why a linac is constructed using progressively longer drift tubes.Answer•The space between the drift tubes is an electric field in which the electrons are accelerated.•Inside a drift tube there is no electric field and this is where the electrons maintain a constant velocity.•To keep the electron bunches evenly spaced, the faster bunches must spend the same amount of time inside the drift tubes as the slower bunches. This means the fasterelectron bunches must travel through longer drift tubes, ensuring that all bunches areaccelerated for the same time interval when they exit the drift tubes in synchronisation.3 marks Mark allocation• 1 mark awarded for each lineTip•These questions are looking for an explanation which demonstrates that you understand the function of the equipment and why it operates in this way. It would not be sufficient to write ‘Because the electrons speed up’ – this would receive 0 marks.Circle the correct word in bold to make the following sentences correct.Conventional X-rays are not as useful as light from a synchrotron of similar wavelength for diagnostic purposes because synchrotron light is[collimated / pulsed / wide spectrum]. Conventional X-rays are always[coherent / incoherent / adherent] and [lower / equal / higher] intensity than synchrotron light.3 marksTips• Synchrotron light is always more intense than traditional X-rays and is of much higherintensity. Synchrotron light can also be collimated. These are all useful traits in diagnostic procedures.Question 8A photon of energy 6.5 eV collides with an electron, and 2.3 eV of energy is transferred to the electron. Calculate the initial and final momentum of the photon. Worked solutionMomentum of photon p = h /λ = hf /c Energy of photon E = hf ⇒ p = E /c19271initial 819271final 86.5 1.610 3.4710kg m s 3104.2 1.610 2.2410kg m s310E p c E p c −−−−−−××===××××===××3 marksMark allocation• 1 mark for the energy of photon equation • 1 mark for each correct answer• Subtract 1 mark if the answers are not in the correct units.An unknown crystalline sample is subjected to X-rays of wavelength 150 pm during Bragg diffraction analysis. The graph shown in Figure 2 was faxed to a researcher but unfortunately some data was obscured.Figure 2Question 9Use the above information to find the crystal layer spacing.Worked solution1210215010remember to halve the 2θvalue from the graph2sin 2sin 322.8310mon d λθ−−××===×2d sin θ = n λ ⇒3 marksMark allocation• 1 mark for halving 2θ from graph• 2 marks for transposition and correct answerQuestion 10Calculate the exact values of the first and third peaks which have been obscured on the graph above.Worked solution 2d sin θ = n λ12111012111011(15010)sin sin sin 222(2.8310)1st peak 11(15010)sin sin (0.265)15.362(2.8310)so 1st peak 2angle 215.3630.723rd peak 33(15010sin o on n n d d n n λλθθθθθ−−−−−−−−−−⎛⎞××⎛⎞=⇒==⎜⎟⎜⎟××⎝⎠⎝⎠⇒=⎛⎞××⇒===⎜⎟××⎝⎠⇒=×=⇒=××⇒=2110)sin (0.795)52.662(2.8310)so 3rd peak 2angle 252.66105.32o oθ−−⎛⎞==⎜⎟××⎝⎠=×=3 marksMark allocation• 1 mark for transposition of formula• 1 mark for each correct answer (first & third peak angles) • If angles not doubled minus 1 markNote consequential error ⎟⎟⎠⎞⎜⎜⎝⎛×××=−−)9.(2)10150(sin 121ans Q n θfor both values.END OF DETAILED STUDY 1DETAILED STUDY 2 – PhotonicsQuestion 1Which of the following diagrams best represents light emitted from a laser?A. B.C. D.2 marks Answer is DTip•Laser light is coherent and of a single wavelength, so all wavetrains are emitted at the same time and are identical in length.A laser beam is shone into the core of a step index fibre with a core refractive index of 1.45 and a cladding refractive index of 1.30, as shown in Figure 1.Figure 1Question 2What is the minimum angle at which a light ray can strike the core–cladding boundary and not enter the cladding?Worked solutionThis is the critical angle:cladding 21core 11.3sin 1.451.3sin 63.7086342'30"6343'1.45c c n n n n θθ−===⇒==°=°=°2 marksMark allocation• 1 mark for recognising this is the critical angle • 1 mark for correct answerQuestion 3What is the greatest value for angle α that will still allow the light beam to remain inside the core?Worked solutionThis is the acceptance angle:111sin sin sin sin 0.64239.9640αα−−−=⇒====°=°3 marksMark allocation• 3 marks for transposition, substitution and correct answerAlternative answer with consequential implications is as follows:Using Snell’s law:n air sin α = n core sin (90o – θc) θc value is answer to Question 2⇒ 1.00× sin α = 1.45 sin (90o – θc)α = 1.45 sin (90o – θc)⇒ sin⇒α = sin–1 [1.45 sin (90o – θc)]Mark allocation for using Snell’s law• 1 mark per lineQuestion 4LEDs all have a ‘band gap’. Describe what the band gap is and what characteristic of the LED it determines.Answer•The band gap is the difference in energy between the electrons in the conduction band and the non-conducting electrons in the valency band.•When an electron in the valency band gains enough energy to jump up to the conduction band, the LED will conduct.•When an electron drops from the conduction band back to the valency band, it will emit its excess energy as a photon.•The difference in energy between the conduction and valency bands is called the band gap energy and this is the amount of energy the emitted photons will have.•The band gap energy determines the characteristic wavelength (colour) of the light emitted from the LED.4 marks Mark allocation• 1 mark per line and the last line is necessary to be awarded full marksQuestion 5A red LED emits light of an average wavelength of 605 nm. While a blue LED emits light of an average wavelength of 470 nm. Find the ratio LEDblue of energy gap Band LEDred of energy gap BandWorked solution777.0605470LED blue of energy gap Band LED red of energy gap Band ====ΔΔ=red blue bluered blue red hc hcE E λλλλ2 marksMark allocation• 2 marks for correct substitution and answerQuestion 6Circle the correct physics term in bold to make the following paragraph correct.An endoscope is a device used by surgeons to view inside the body duringkeyhole surgery. Light is transmitted through bundles of [incoherent / coherent / linear] optic fibres to the operational end of the endoscope. This light undergoes [reflection / refraction / total internal reflection] inside the body cavity. Some of this light then passes through a focusing [mirror / lens / prism] beforeentering a set of [incoherent / coherent / linear] optic fibres which transmit the light using the principal of [reflection / refraction / total internal reflection] to the viewing eyepiece as an accurate [picture / reflection / image] of the body cavity.3 marksMark allocation• Half a mark awarded for each correct term.。

托马斯杨的光干涉实验双语文稿演示

2021/3/13
10
二、定量分析
s
s1
d o
q
r1
q r2
s 2 r
D
B
x
o
波程差可写为：r2r1dsinq
式中q 是B点到双缝中心的连线与水平方向之间的夹角
因q 很小， sinqtgqx/D
d x
D
2021/3/13
11
1、干涉加强的条件为：
dxk (k0,1,2,)
D
屏上产生明条纹的位置为：
• 假如你认为光是波
，准备通过哪些物理现象来证明呢？
一、实验
1 、实验装置
S1ቤተ መጻሕፍቲ ባይዱ
r1
Sd
P
r2
x
o
S2
D
单色光：只有单一波长的光。
S1和S2之间的距离很小（约为0.2mm），观察屏与狭缝之间的距离约为1m以上。
2021/3/13
9
2、条纹分布观察屏上出现一系列稳定的、对称的明暗相
间条纹，条纹间的距离彼此相等，且都与狭缝平行，O处的中央条纹是明条纹。
托马斯杨的光干涉实验双语文稿演示
（优选）托马斯杨的光干涉实验双语
1801年，英国物理学家托马斯·杨（1773~1829）
光在实验室里成功的观察到了光的干涉．
的
托马斯·杨（Thomas Young，1773～1829 ）英国
干医生、物理学家，光的波动说的奠基人之一。
涉
Thomas Young (Thomas
心位置不变，其它各级条纹相应向中央明纹靠近，条
纹变密。反之，条纹变稀疏。
xxk1
xk
D
d
x k D

英语光学调研报告

英语光学调研报告Optical Research ReportIntroduction:The purpose of this research report is to explore the field of optics, which is a branch of physics that deals with the behavior and properties of light. We will examine various aspects of optics, including its applications, techniques, and recent advancements. By the end of this report, the readers will have a better understanding of the impact and significance of optics in various fields.1. History of Optics:Optics has a long history that dates back to ancient civilizations. The early Greeks, such as Euclid and Ptolemy, laid the foundations of geometrical optics. Later, in the 17th century, scientists like Isaac Newton and Christiaan Huygens made significant contributions to the study of optics. Newton's experiments with prisms and Huygens' wave theory of light paved the way for further developments in the field.2. Basic Principles of Optics:Optics involves the study of light, which can be defined as an electromagnetic radiation that is visible to the human eye. It exhibits both particle-like and wave-like properties. The basic principles of optics include reflection, refraction, diffraction, and interference. Understanding these principles is crucial in understanding how light interacts with various materials and devices.3. Applications of Optics:Optics finds applications in numerous fields, including telecommunications, medicine, astronomy, and microscopy. In telecommunications, optical fibers are used for transmitting large amounts of data over long distances. In medicine, optics is used in devices like endoscopes and LASIK surgery. In astronomy, telescopes use optics to observe celestial objects. Microscopes utilize optics to visualize small samples and explore the microscopic world.4. Techniques in Optics:Several techniques are employed in optics to manipulate and analyze light. Some common techniques include spectroscopy, imaging, and holography. Spectroscopy involves the study of the interaction between light and matter, providing valuable information about the composition and properties of materials. Imaging techniques, such as lenses and mirrors, are used to create accurate representations of objects. Holography allows the recording and reproduction of three-dimensional images using interference patterns.5. Recent Advancements in Optics:Optics has witnessed numerous advancements in recent years. One such advancement is the development of metamaterials, which have unique properties not found in natural materials. These materials have applications in areas like cloaking devices and super lenses. Another breakthrough is the development of quantum optics, which explores the interaction of light with quantum systems. This field has promising applications in quantum computing and cryptography.Conclusion:In conclusion, optics is a fascinating field of study that has a significant impact on various sectors of society. Its rich history, basic principles, applications, techniques, and recent advancements make it a vital discipline in the scientific world. As technology continues to advance, the possibilities for further developments in optics are endless. Further research and exploration in this field will undoubtedly lead to new discoveries and innovations that will continue to shape our understanding of light and its applications.。

1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。

a r X i v :a s t r o -p h /0606152v 1 7 J u n 2006Mon.Not.R.Astron.Soc.000,1–13(2002)Printed 5February 2008(MN L A T E X style ﬁle v2.2)Shapley Optical Survey II:The eﬀect of environment onthe colour-magnitude relation and galaxy colours ⋆C.P.Haines,1⋆⋆P.Merluzzi,1A.Mercurio,1A.Gargiulo,1N.Krusanova,1G.Busarello, Barbera,1and M.Capaccioli 1,21INAF -Osservatorio Astronomico di Capodimonte,via Moiariello 16,I-80131Napoli,Italy2Departmentof Physics,Universit`a “Federico II”,Napoli,ItalyAccepted 1988December 15.Received 1988December 14;in original form 1988October 11ABSTRACTWe present an analysis of the eﬀects of environment on the photometric properties ofgalaxies in the core of the Shapley Supercluster at z =0.05,one of the most massive structures in the local universe.The Shapley Optical Survey (SOS)comprises archive WFI optical imaging of a 2.0deg 2region containing the rich clusters A3556,A3558and A3562which demonstrate a highly complex dynamical situation including ongoing cluster mergers.The B −R/R colour-magnitude relation has an intrinsic dispersion of 0.045mag and is 0.015±0.005mag redder in the highest-density regions,indica-tive of the red sequence galaxy population being 500Myr older in the cluster cores than towards the virial radius.The B −R colours of galaxies are dependent on their environment,whereas their luminosities are independent of the local density,except for the very brightest galaxies (M R <−22).The global colours of faint ( M ∗+2)galaxies change from the cluster cores where ∼90%of galaxies lie along the cluster red sequence to the virial radius,where the fraction has dropped to just ∼20%.This suggests that processes related to the supercluster environment are responsible for transforming faint galaxies,rather than galaxy merging,which should be infrequent in any of the regions studied here.The largest concentrations of faint blue galaxies are found between the clusters,coincident with regions containing high fractions of ∼L ∗galaxies with radio emission indicating starbursts.Their location suggests star-formation triggered by cluster mergers,in particular the merger of A3562and the poor cluster SC 1329-313,although they may also represent recent arrivals in the superclus-ter core complex.The eﬀect of the A3562-SC 1329-313merger is also apparent as a displacement in the spatial distribution of the faint galaxy population from both the centres of X-ray emission and the brightest cluster galaxies for both systems.The cores of each of the clusters/groups are marked by regions that have the lowest blue galaxy fractions and reddest mean galaxy colours over the whole supercluster region,conﬁrm-ing that star-formation rates are lowest in the cluster cores.In the cases of A3562and SC 1329-313,these regions coincide with the centres of X-ray emission rather than the peaks in the local surface density,indicating that ram-pressure stripping may have an important role in terminating any remnant star-formation in galaxies that encounter the dense ICM of the cluster cores.Key words:Galaxies:clusters:general —Galaxies:clusters:individual:Shapley supercluster —Galaxies:photometry —Galaxies:evolution1INTRODUCTIONThe cluster galaxy population has evolved rapidly over the last 4Gyr (e.g.,Butcher &Oemler 1978,1984;Dressler et al.1994,1997;Treu et al.2003;Kodama et al.⋆Based on European Southern Observatory archive data⋆⋆E-mail:chris@na.astro.it2004).Clusters at z 0.4are dominated,particularly at faint magnitudes,by blue spiral galaxies,predominantly ir-regular or Sc–Sd spirals.Some of these show signs of dis-turbed morphologies,and many present spectroscopic ev-idence that they have undergone multiple star-formation events over the last 1–2Gyr (Dressler et al.1994).Con-versely,local clusters are completely dominated by passive2 C.P.Haines et al.early-type galaxies:elliptical and lenticular(S0)galaxies at the brighter end,and dwarf spheroids at fainter magnitudes.In the standard hierarchical cosmological model,z∼0.4 represents the peak infall rate ofﬁeld galaxies onto the clus-ter(Kauﬀmann1995),and it is the transformation of these infallingﬁeld galaxies from star-forming disk-dominated galaxies into passively-evolving spheroids over a period of 4–5Gyr through their encounter with the cluster envi-ronment,that produces the observed changes in cluster galaxy populations.Several physical mechanisms related to the cluster environment have been proposed as producing the observed transformations in galaxies,in which inter-actions with either other cluster galaxies or the hot intra-cluster medium(ICM)aﬀect both their structural and star-formation properties.To distinguish between these mechanisms it is necessary to examine both where the transformations occur,and how the star-formation and structural properties of the galax-ies are changed(e.g.Treu et al.2003).For example,ram pressure from the passage of the galaxy through the dense ICM can eﬀectively remove the cold gas supply and thus rapidly terminate new star-formation,either by stripping the gas directly(Abadi,Moore&Bower1999),or by in-ducing a starburst in which all of the gas is consumed (Fujita&Nagashima1999).The most dramatic ICM-galaxy interactions should occur when two clusters merge,as shock fronts created in the ICM may trigger starbursts in galaxies over large scales(Roettiger,Burns&Loken1996).Impor-tantly,in terms of their environmental eﬀects,these mech-anisms all require a dense ICM,and so their evolutionary eﬀects are limited to the cores of clusters.In contrast,galaxy mergers,which can strongly af-fect the morphological evolution of disks,cannot occur when the encounter velocities are much greater than the internal velocity dispersion of galaxies(Aarseth&Fall 1980),and so while frequent in small groups,are rare in rich clusters(Ghigna et al.1998).Alternatively galaxy ha-rassment,whereby repeated close(<50kpc),high-velocity (>1000km s−1)encounters with massive galaxies and the cluster’s tidalﬁeld cause impulsive gravitational shocks that damage the fragile disk of late-type spirals(Moore et al. 1996),transforming them over a period of several Gyr. Galaxy harassment is eﬀective throughout a cluster,includ-ing beyond the virial radius,but its eﬀects should be greater for those clusters with higher velocity dispersions.Finally,when a galaxy falls into a more massive halo,the diﬀuse gas in its halo is lost to the ICM,thus preventing further cooling and replenishment of the cold gas supply,“suﬀocating”the galaxy(e.g.Blanton et al. 2000;Diaferio et al.2001).Star-formation in the galaxy then declines slowly as the remaining cold gas is used up (Larson,Tinsley&Caldwell1980).The large datasets provided by the2dFGRS and SDSS have allowed the environmental eﬀects on galaxy properties to be followed statistically over the full range of environ-ments,from the sparseﬁeld to the dense cluster cores(e.g. Lewis et al.2002;G´o mez et al.2003),at least for the bright-est galaxies(M<M∗+1).They show that star-formation is most closely dependent on local density,and is system-atically suppressed above a critical value of density,that is found3–4virial radii from clusters,but also in galaxy groups as poor asσ∼100km s−1.This suppression is ob-served to be independent of the richness of the structure to which the galaxy is bound(Tanaka et al.2004),indicating that mechanisms such as galaxy harassment or ram-pressure stripping are not important for the evolution of bright galax-ies.Instead the strongest candidates for driving their trans-formation are galaxy suﬀocation and low-velocity encoun-ters,which are eﬀective in both galaxy groups and cluster infall regions.However,it is not clear if and how this scenario ex-tends to fainter magnitudes,as there has been observed a strong bimodality in the properties of galaxies about a characteristic stellar mass∼3×1010M⊙(corresponding to ∼M∗+1),with more massive galaxies predominately pas-sive red spheroids,and less massive galaxies tending to be blue star-forming disks(Kauﬀmann et al.2003).This bi-modality implies fundamental diﬀerences in the formation and evolution of giant and dwarf galaxies,and it has been proposed(e.g.Dekel&Birnboim2006;Kereˇs et al.2005) that these are driven by thermal processes in the gas inﬂow-ing from the halo onto the galaxy,with the characteristic mass scale representing the point at which shocks in the halo become stable,heating up the halo gas,and preventing further cooling.Hence if the formation and evolution of gi-ant and dwarf galaxies are so fundamentally diﬀerent,then they are likely to be aﬀected diﬀerently by mechanisms re-lated to the environment.For example,galaxy harassment should be most eﬃcient at transforming low-luminosity late-type galaxies.Tanaka et al.(2004)ﬁnd diﬀerences in the environmental dependences of faint(M∗+1<M<M∗+2) and bright(M<M∗+1)galaxy populations,and suggest that faint galaxies are aﬀected by mechanisms related to the structure in which the galaxy is found.To understand the mechanisms underlying the trans-formation of faint galaxies requires datasets reaching much fainter luminosities.Crucial discriminators between the diﬀerent transformation mechanisms are the time-and distance-scales involved:while ram-pressure stripping should rapidly terminate star-formation in a galaxy within 100Myr but requires the dense ICM of the cluster core;a galaxy undergoing suﬀocation will have its star-formation rate slowly decline over a period of several Gyr.Hence the nature of the transition from regions where the majority of galaxies are star-forming,and those dominated by passive galaxies,will depend strongly on the dominant mechanism involved.One approach is to use galaxy colours,which can be readily obtained to much fainter magnitudes than spectro-scopic star-formation rates,and which through the use of models can be directly related to star-formation histories with minimal assumptions(e.g.Bruzual&Charlot2003). Recent large datasets have shown that the bimodality of galaxies is also manifested through their broadband photom-etry,in particular a separation can be made on the basis of colour into red and blue galaxy populations(Strateva et al. 2001;Blanton et al.2003),which correspond roughly to the two broad types previously known from their morphological and spectroscopical characteristics:passively-evolving early-type and star-forming late-type galaxies.This bimodality has been further quantiﬁed,resulting in colour-magnitude (C-M)relations and for both the red and blue galaxy pop-ulations(Baldry et al.2004),and its evolution observed to z∼1(Bell et al.2004).Balogh et al.(2004)show that theShapley Optical Survey II3bimodal galaxy colour distribution is strongly dependent on environment,with the fraction of galaxies in the red distri-bution at aﬁxed luminosity increasing from10–30%in the lowest density environments,to∼70%at the highest densi-ties.The most dramatic eﬀects of environment on galaxy evolution should occur in superclusters,where the infall and encounter velocities of galaxies are greatest(>1000km s−1), groups and clusters are still merging,and signiﬁcant num-bers of galaxies will be encountering the dense ICM of the cluster environment for theﬁrst time.With this in mind we are undertaking the Shapley Op-tical Survey(SOS),an optical photometric study of the core region of the Shapley supercluster(Shapley1930),one the most massive structure in the local universe,containing as many as25Abell clusters.In this paper we examine the eﬀect of the supercluster environment on the star-formation histories of galaxies as measured through their galaxy colours.We present the SOS in Section2,and then describe how we quantify the local environment and statistically subtract theﬁeld galaxy pop-ulation in Sections3and4.We present our analysis of the C-M relation in Section5,which then allows us to separate the red and blue galaxy populations whose spatial distri-butions are presented in Section6.We examine the envi-ronmental dependencies on galaxy colours in Section7,and discuss ourﬁndings in Section8,before presenting our con-clusions in Section9.Throughout the paper we adopt a cos-mology withΩM=0.3,ΩΛ=0.7and H0=70km s−1Mpc−1. According to this cosmology1arcmin corresponds to60kpc at z=0.048.2THE SHAPLEY OPTICAL SUR VEYThe SOS comprises wide-ﬁeld optical imaging of a2.0deg2 region covering the whole of the Shapley supercluster core(hereafter SSC),which comprises three Abell clusters A3556,A3558and A3562and two poor clusters SC1327-312 and SC1329-314.The resultant galaxy catalogues are com-plete to R=22.0and B=22.5,allowing us for theﬁrst time to study the eﬀect of the supercluster environment on the photometric properties of galaxies,particularly the dwarf galaxy population where we reach M∗+7.The area is covered by extensive redshift surveys (e.g.Bardelli et al.2000;Quintana,Carrasco&Reisenegger 2000;Drinkwater et al.2004)which indicate that these clus-ters form a complex clumpy and highly-elongated struc-ture∼9h−170Mpc across,which is in theﬁnal stages of collapse,with infall velocities reaching2000km s−1 (Reisenegger et al.2000).There exists a wealth of multi-wavelength data from radio(ler2005)to X-ray(e.g. Finoguenov et al.2004),which in conjunction with the red-shift data,describe a dramatic scenario with ongoing cluster-cluster mergers triggering star-formation in galaxies over ∼Mpc scales.It is clear that amid this maelstrom of galax-ies,groups and clusters,both galaxy harassment and ram pressure stripping should be at their most eﬀective in trans-forming the infallingﬁeld galaxies.We aim to use the SOS dataset to study the eﬀect of en-vironment on the luminosity distribution,colours and struc-tural properties of galaxies,and through comparison with numerical simulations and theoretical predictions,draw in-sights regarding which physical processes are most impor-tant for the transformation and evolution of galaxies in these environments.In Mercurio et al.(2006,hereafter Paper I)we intro-duce the survey,and describe the observations,calibrations, and derivation of the galaxy catalogues.The galaxy lu-minosity functions are also presented,and signiﬁcant en-vironmental eﬀects are observed,in the form of a dip at ∼M∗+2which becomes deeper,and a faint-end slope which becomes steeper,with decreasing density.We explain these results in terms of the galaxy harassment scenario,in which the late-type spirals that represent the dominant popula-tion at∼M∗+2are transformed by galaxy harassment into passively-evolving dwarf spheroids,and in the process be-come∼1–2magnitudes fainter due to mass loss and an age-ing stellar population without new star-formation.In this paper we examine the eﬀect of the superclus-ter environment on the star-formation histories of galaxies as measured through their galaxy colours,while in future papers we expect to consider the environmental impact on galaxy structural parameters and compare our observational results with semi-analytical models of galaxy evolution in n-body simulations of a supercluster region.The data were obtained from the ESO science archive (68.A-0084,P.I.Slezak),comprising wide-ﬁeld B-and R-band imaging covering a2.0deg2region towards the clusters A3562,A3558and A3556which form the core of the Shap-ley supercluster at z∼0.05.Full details of the observations, data reduction,and the production of the galaxy catalogues are described in Paper I,and only a summary is presented below.The observations were made from March2002to April 2003using the WFI camera,an instrument made up of eight 2046×2048CCDs giving aﬁeld of view of34′×33′,and which is set at the Cassegrain focus of the2.2-m MPG/ESO telescope at La Silla.The survey is made up of eight contigu-ousﬁelds,each with total exposure times of1500s in B and 1200s in R,and typical FWHMs of0.7–1.0′′.The data are reduced using the ALAMBIC pipeline(version1.0,Vandame 2004),and calibrated to the Johnson-Kron-Cousins photo-metric system using observations of Landolt(1992)stan-dard stars.The sources are then extracted and classiﬁed us-ing SExtractor(Bertin&Arnouts1996),resulting in galaxy catalogues which are both complete and reliable(i.e.free of stars)to R=22.0and B=22.5.For this analysis we con-sider only galaxies to R=21.0where uncertainties in the photometry are less than0.1mag in both R and B−R for galaxies belonging to the supercluster.3QUANTIFYING THE GALAXYENVIRONMENTTo study the eﬀect of the cluster environment on galaxies in the SSC,the local density of galaxies,Σ,is determined across the SOS mosaic.This is achieved using an adaptive kernel estimator(Pisani1993,1996),in which each galaxy i is represented by a Gaussian kernel,K(r i)∝exp(−r2/2σ2i), whose width,σi is proportional toΣ−1/2ithus matching the resolution locally to the density of information available. For this study,we consider the surface number density of4 C.P.Haines et al.Right Ascension (J2000)D e c l i n a t i o n (J 2000)Figure 1.The surface density of R <21.0galaxies in the region of the Shapley Supercluster core complex.Isodensity contours are shown at intervals of 0.25gals arcmin −2,with the thick contours corresponding to 0.5,1.0and 1.5gals arcmin −2,the densities used to separate the three cluster environments.High-density regions (Σ>1.5)are indicated by red colours,while intermediate-(1.0<Σ<1.5)and low-density (0.5<Σ<1.0)regions are indicated by yellow/orange and green colours respectively.The centres of X-ray emission for each of the clusters are indicated.R <21.0(<M ∗+6)galaxies,with an additional colour cut applied to reject those galaxies more than 0.2mag redder in B −R than the observed cluster red sequence to minimize background contamination.As there are no known struc-tures in the foreground of the SSC (90%of R <16galax-ies have redshifts conﬁrming that they belong to the su-percluster),any substructure identiﬁed in the density map is likely to be real and belonging to the supercluster.The local density is initially determined using a ﬁxed Gaussian kernel of width 2arcmin,and then iteratively recalculated using adaptive kernels.The resultant surface density map of the SSC is shown in Fig 1,with the three clusters and two groups indicated.Isodensity contours are shown at intervals of 0.25gals arcmin −2,with the thick contours correspond-ing to 0.5,1.0and 1.5gals arcmin −2,the densities used to separate the three cluster environments described below.The expected density of ﬁeld galaxies is estimated through analysis of thirteen 35′×35′ﬁelds of deep BV R imaging taken from the Deep Lens Survey (DLS;Wittman et al.2002).These data covering 4.3deg 2in total,were taken using the Mosaic-II cameras on the NOAO KPNO and CTIO 4-m telescopes,and have 5σdepths of B,V,R ∼27and typical R -band FWHMs of 0.9′′,allowing accurate photometric measurements and star-galaxy classiﬁcations to be made to at least the depths of our survey.Through applying the same colour-magnitude cuts,we estimate the density of ﬁeld galaxies to be 0.335±0.019gals arcmin −2,and hence the thick con-tours correspond to overdensity levels of ∼50,200and400gals h 270Mpc−2respectively.The entire region covered by the SOS can be seen to be overdense with respect to ﬁeldgalaxy counts.For the following analyses on the eﬀect of the cluster environment on its constituent galaxy population we de-ﬁne three regions selected according the local surface num-ber density.Firstly we consider a high-density region with Σ>1.5gals arcmin −2which correspond to the cores of the clusters.Next we consider intermediate-(1.0<Σ<1.5)and low-density (0.5<Σ<1.0)regions which probe the ﬁla-ment connecting the clusters A3562and A3558,as well as the wider envelope containing the whole supercluster core complex.4STATISTICAL FIELD GALAXY SUBTRACTIONTo accurately measure the global photometric properties of the galaxy population in the SSC requires the foreground /background contamination to be estimated eﬃciently and corrected for.There exists already a wealth of spectroscopic data in the region,comprising 607published galaxy red-shifts (Bardelli et al.1998)corresponding to 90%of R <16galaxies,dropping to 50%for R <17.7.For those galaxies without redshifts,particularly at fainter magnitudes,we es-timate the probability that they are supercluster members.This probability is dependent on the spatial position,the R -band magnitude and B −R colour.The dependence on its spatial position,through its local number density,is clear as galaxies towards one of the density peaks will be moreShapley Optical Survey II5 likely to be members than those in regions where the sur-face density is closer to that expected for theﬁeld.The de-pendence on the galaxies colour and magnitude is complex,with galaxies located on the cluster red sequence most likelyto be members,while those galaxies much redder than thesequence most likely to belong to the background popula-tion.It is important that all three parameters are consideredsimultaneously,as the relationship between the broad-bandproperties of galaxies and their environment has been shownto be complex(Blanton et al.2003).We account for this by considering separately the threecluster environments described previously when estimat-ing the probability that galaxies are supercluster membersthrough their R-band magnitude and B−R colour using themethods described in Kodama&Bower(2001).For each ofthese three cluster environments and the Deep Lens Surveyﬁeld comparison,two-dimensional histograms are built withbins of width0.4mag in R and0.2mag in B−R to properlymap the galaxy C-M distribution.The histogram ofﬁeldgalaxies is normalised to match the area within each clusterregion,and for each galaxy,the probability that galaxy ibelongs to the supercluster is then deﬁned as:ΣSC(R,B−R)i−Σf ield(R,B−R)iP i SC=6C.P.Haines et al.−0.60−0.40−0.20 0.00 0.20d(B−R)G a l a x i e sFigure 3.The distribution of B −R galaxy colours oﬀsets from the C-M relation predicted by the biweight algorithm for R <19galaxies with local densities greater than 1.0gal arcmin −2.by sampling n galaxies with replacement according to theprobabilities P iSC calculated using Eq. 1.Babu &Singh (1983)have analytically estimated that ∼n log 2n bootstrap resamplings give a good approximation to the underlying density population.The resultant best-ﬁtting C-M relation is found to be:(B −R )CM =2.3312±0.0026−0.0564±0.0037×R,(2)where the quoted uncertainty in the intercept assumes a ﬁxed value of slope.The obtained dispersion about the re-lation as given by the biweight scale of the deviations is 0.0738±0.0041mag.As a robust test of the results obtained using the bi-weight algorithm,we plot a histogram of the distribution of ∆(B −R )CM ,the B −R galaxy colour oﬀset from the C-M relation,and model the distribution as a sum of two Gaus-sian functions,one to represent the red sequence,and an-other to represent the “blue cloud”population.Fig 3shows that a bimodal Gaussian distribution describes well the dis-tribution of ∆(B −R )CM (χ2/ν≈1),but with a mean oﬀ-set of 0.0069±0.0027mag with respect to the biweight me-dian,and a dispersion of 0.0453±0.0019mag that is signif-icantly smaller than predicted by the biweight scale estima-tor,and comparable to the 0.054mag dispersion observed for the Coma cluster in the same passbands (L´o pez-Cruz et al.2004).Hence despite iteratively clipping galaxies >3σfrom the median value of the relation,both the intercept and dispersion of the relation obtained using the biweight algo-rithm have been aﬀected by outliers and the heavily skewed distribution.We do not expect that photometric uncertainties are a major contributor to the observed dispersion as:ﬁrstly the mean B −R uncertainty for galaxies in the red sequence is found to be 0.012mag,only reaching 0.025mag by R =19.0;R <21galsχ2Σ>1.0+0.0069±0.00270.0453±0.00190.99Table 1.Gaussian ﬁts to the B −R colour distribution around the C-M relation for R <19galaxies in the diﬀerent density en-vironmentsand secondly the observed dispersion does not vary signiﬁ-cantly as a function of magnitude over 14.5<R <19.It is remarkable that such a small dispersion is obtained,given the large number of galaxies involved (∼600)over two orders of magnitude in luminosity,and spread across three rich clusters and ∼9h 70Mpc.The wide spread of redshifts within the supercluster complex (0.035<z <0.056)could introduce a signiﬁcant component to the observed disper-sion through the spread of k-corrections required for the red sequence galaxies,as the predicted change in the B −R k-correction of an elliptical galaxy from 0.035to 0.056is ∼0.08mag (Poggianti 1997),as is the observed increase in B −R colour of red sequence galaxies (L´o pez-Cruz et al.2004).To measure the possible eﬀect of k-corrections on the obtained colour dispersion of red sequence galaxies,we con-sider those red sequence galaxies with known redshifts.Al-though the redshift data is less than 50%complete beyond R =17.7,the B −R colour dispersion of the red sequence galaxies with redshifts is consistent with that for the whole R <19sample.After applying suitable k-corrections to each of the galaxies with known redshifts,and the colour dis-persion about the red sequence is recalculated,found to be still consistent with that before the k-correction has been applied.Hence the observed internal dispersion of galaxy colours around the red sequence is not primarily the ef-fect of diﬀerent k-corrections over the redshift range of the supercluster.This can be explained by considering that the redshift distribution has a standard deviation of 0.0036(∼1100km s −1),corresponding to an rms σof ∼0.014mag in B −R ,signiﬁcantly smaller than the observed σCM .To examine the eﬀect of environment on the colour of the C-M relation we ﬁt bimodal Gaussian distributions to the ∆(B −R )CM distribution in the three environments as parametrised by the local R <21galaxy density.The slope and zero-point are maintained ﬁxed at the values indicated in Eq.2,in order to measure the shifts in the overall B −R colour of the red sequence with environment.We do not make any attempt to determine the slope and intercept in the diﬀering environments using the biweight algorithm,as the eﬀect of the heavily skewed distribution on the deter-mination of these values will be dependent on environment,due to the increasing blue galaxy fraction from high-to low-density regions.Hence the resulting ﬁts would be biased by the changing blue galaxy population,and mask any inherent changes in the red sequence population with environment.The results of the Gaussian ﬁts to the red sequence pop-ulation are shown in Table 1.In each case the galaxy colour distribution is well described by a double Gaussian function.Shapley Optical Survey II7Right Ascension (J2000)D e c l i n a t i o n (J 2000)Figure 4.The surface density of R <21galaxies >3σbluer than the cluster red sequence (blue ﬁlled contours)and those within 3σof the cluster red sequence (red contours)over the supercluster core complex.The isodensity contours for the blue galaxies are shown at intervals of 0.125gals arcmin −2,while the red contours are at intervals of 0.25gals arcmin −2.The centres of X-ray emission for each of the clusters are indicated.The zero-points of the red sequence are consistent for the low-and intermediate-density regions,but the red sequence is found to be 0.0147mag redder in the high-density region,a result signiﬁcant at the 2.6σlevel.The redward shift of the red sequence continues if the density threshold is increased further,reaching 0.0195mag for Σ>2.0.The B −R colour dispersion of the red sequence remains constant at ∼0.045,for each of the environments,suggesting that the observed reddening indicates an overall shift in the red galaxy popu-lation,rather than a broadening of the distribution due to increased numbers of bluer galaxies.6THE SPATIAL DISTRIBUTION OF RED AND BLUE GALAXIESTo examine where star-formation has been triggered or in-hibited by the supercluster environment,we split the galaxy population into two according to colour.We identify red galaxies as those within 3σ(after including photometric un-certainties)of the cluster red sequence,and blue galaxies as those >3σbluer than the red sequence.Hence these blue galaxies are all those not belonging to the red sequence,due to being either currently having some star-formation,or having had some in the previous ∼2Gyr.Figure 4shows the spatial distribution of both red and blue galaxies over the supercluster complex,after correct-ing for the expected background contribution of 0.147and 0.071gals arcmin −2for the red and blue galaxy subsets re-spectively,as estimated from the 13Deep Lens Survey ﬁelds.The blue isodensity contours for the blue galaxies are shown at intervals of 0.125gals arcmin −2,which are ﬁlled with in-creasingly intense blue colours with density.Overlaid are the red isodensity contours at intervals of 0.25gals arcmin −2to represent the local density of the red galaxy population.Note that all the contours indicate overdensities in compar-ison to the ﬁeld,and that the spacing of the contours for the red galaxy population is twice that of the those for their blue counterparts.The centres of the X-ray emission from each of the clusters in the region are indicated.The spatial distribution of the red and blue galaxy pop-ulations diﬀer signiﬁcantly.Whereas the blue galaxies ap-pear reasonably evenly spread across the whole ﬁeld,the red galaxies are highly concentrated towards the cluster centres and the ﬁlamentary structure connecting A3562and A3558.In contrast,none of the three Abell or two poor clusters show particular overdensities in the blue galaxy distribu-tion towards their cores,in fact they appear underdense in comparison to their immediate surroundings,as noted by Metcalfe et al.(1994)in the case of A3558.However,several localised overdensities of blue galaxies are apparent along the ﬁlamentary structure connecting A3562and A3558,in-dicative of regions of enhanced star-formation within the supercluster core complex.What is particularly interesting is their distribution within the ﬁlamentary structure with re-spect to the clusters.The most overdense regions are located between each of the clusters A3562,A3558and the two poor clusters.The two most notable overdensities of blue galaxies appear to be the western ﬂank of the poor cluster SC 1329-313,and a linear structure bisecting the clusters A3558and SC 1327-312.Both these overdensities contain numer-ous blue galaxies which are spectroscopically conﬁrmed as belonging to the supercluster.The region where these over-densities of blue galaxies are located is where the two clus-。

Shapley Optical Survey II The effect of environment on the colour-magnitude relation and ga

中考英语书面表达议论文论证过程单选题40题

矢量光束Cylindrical vector beams from

刺激-反应联结学习在项目特异性比例一致效应中的作用

优美斯（Optimax Systems）的相位平移干扰光学测量方法白皮书说明书

大学-光学的培训教材

TPO38托福阅读答案解析

AXIS P1465-LE 2 MP 全能防盗摄像头说明书

Question

热红外传感史

光学效应英语作文

重庆市巴蜀中学2023-2024学年高二上学期期中英语试卷

太空镜子的利弊英语作文

The properties of optical coatings

光学效应 英语作文

用科学解决近视的600字英语作文

浅水效应英语

关于障眼法的英语作文

INSIGHT Physics Trial Exam 2 Solutions Book - 2006

托马斯杨的光干涉实验双语文稿演示

英语光学调研报告

光学效应英语作文