天津大学物理光学.pptVIP

第十章光的电磁理论基础MeasurementsoftheSpeedoflight本课内容回顾1、波的叠加原理2、两个频率相同、振动方向相同的单色光波叠加3、驻波（频率同、振动方向同、传播方向相反）4、两个频率相同、振动方向垂直的单色光波叠加5、光学拍（小频率差、振动方向同、传播方向同、振幅同）6、相速度和群速度InterferencefringesKeywords1.Pathdifference2.Phasedifference3.Theorderofinterference4.Thelightdistribution5.Amaximumamountoflight(maxima)6.Aminimumamountoflight(minima)Homework(11-12)Lightpassesthroughtwonarrowslitsofd=0.8mm.Onscreen1.6mawaythedistancebetweenthetwosecond-ordermaximais5mm.Whatisthewavelengthofthelight?P24312干涉现象（Interference）在两个（或多个）光波叠加的区域形成强弱稳定的光强分布的现象，称为光的干涉现象。ThomasYoung(1773-1829)ABritishphysicianandphysicist.Hecouldreadatage2,at6beganstudyingLatin,andat13hadalsomasteredGreek,Hebrew,ItalianandFrench.At19heenteredmedicalschool,correctlyexplainedtheaccommodationoftheeyeandwaselectedFellowoftheRoyalSociety.In1796,hegraduatedfromtheUniversityofGottingenMedicalSchool,openedapracticeinLondon,and5yearslaterbecameprofessorofNaturalPhilosophyattheRoyalInstitution.Thatsameyear,1801,hereadthefirstofseveralpaperspresentingthewavetheoryoflightandtheprincipleofinterference,muchtotheoppositionofNewton’sfollowers.Youngmadenoteworthycontributionsalsotoacoustics,atmosphericrefraction,elasticity,fluiddynamicsandcolorvision.InterferencefringesThelightofdistributionresultingfromasuperpositionofwaveswillconsistofalternatelybrightanddarkbandscalledinterferencefringes.Suchfringescanbeobservedvisually,projectedonascreen,orrecordedphotoelectrically.PartialCoherencecontrastItisincorrecttothinkoflightaseithercoherentorincoherent.Lightcanhavedifferentdegreesofcoherence,whichintroducedtheconceptofpartialcoherence.Completecoherenceismerelyatheoreticallimit.PartialCoherencecontrastAssumethattwowavetrainsoflight,eachoffinitelength?s,