光的干涉optics03.film interference

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1、Amplitude-splittingInterferometers§7.4.1DielectricFilms-Double-BeamInterference(Thin-FilmInterference)§7.4.2MirroredInterferometersContentsThin-filminterference1.Fringesofequalinclination2.Fringesofequalthickness:wedgethin-filmandNewton’srings.Mirroredin

2、terferometers1.Michelsoninterferometer2.Mach-Zehnderinterferometer3.Sagnacinterferometer.Teachingpurpose:知道各干涉仪的装置，会画出示意图；会计算两束反射光（或折射光）之间的光程差，并讨论干涉花纹；会利用干涉仪进行微小测量，波长测量等。Newwords1.TheindexofrefractionandthespeedoflightTheindexofrefractionofamediumistherat

3、ioofthespeedoflightinvacuumtoitsspeedinthetransparentmedium.Thefrequencyofthelightisthesameinbothmedium.thenFringesofequalinclination2.EquivalentpathdifferenceandphasedifferenceEquivalentpath=geometricalpath×indexofrefractionFringesofequalinclinationOptic

4、alpath光程=n×rOpticalpathdifference光程差δ=n2r2-n1r1Phasedifference=2π×δ/λ0n1n2S2S1r2r1pFringesofequalinclination3.thin-filminterference---amplitudedivisionMediumn1,n3Thin-filmn2,dIncidentlight,λ,i,rReflectlight2and3iscoherent.Transmissionlight4and5iscoherent.

5、FringesofequalinclinationOpticalpathdifferenceofreflectlight2,3PhasedifferencePhasechangesuponreflectionmustbedoneonacase–by-casebasisFringesofequalinclinationOpticalpathdifferenceoftransmissionlight4,5PhasedifferenceFringesofequalinclination①phasechanges

6、uponreflection②ifi=0,Phasedifference=PhasedifferenceReflectionlighthasphasechangeTransmissionlighthasphasechangeFringesofequalinclinationFringesofequalthicknessInourdailylifethecolorfringesonanoilfilmoronasoapbubbleareoftenseen.Thesearecommonexamplesofint

7、erferencetakingplaceinthinfilm.1.wedgethin-filmOpticalpathdifferenceFringesofequalthicknessTheinterferencefringestraceoutcontoursofconstantthicknessofthewedgethin-film.Thethicknessdifferencebetweenadjacentbright(dark)fringesThefringeswidth(spacebetweenadj

8、acentdarkfringes)FringesofequalthicknessExample1:Abroadbeamofredlight,withwavelengthλ=632.8nm,incidencesonamairwedgeasshowninfigure.Anobserverlookingdowmontheblockwiththeairwedgeseesaninterferencepatternconsistingof