迈克尔逊干涉仪测空气的折射率赵龙宇PB06005068一、实验目的用分离的光学元件构建一个迈克尔逊干涉仪。通过降低空气的压强测量其折射率。二、仪器和光学元件光学平台；HeNe激光；调整架，35x35mm；平面镜，30x30mm；磁性基座；分束器50:50；透镜，f=+20mm；白屏；玻璃容器，手持气压泵，组合夹具，T形连接，适配器，软管，硅管三、实验原理借助迈克尔逊干涉仪装置中的两个镜，光线被引进干涉仪。通过改变光路中容器内气体的压强，推算出空气的折射率。IftwoWaveshavingthesamefrequencyω,butdifferentamplitudesanddifferentphasesarecoincidentatonelocation,theysuperimposetoY=a1⋅sin(wt−α1)+a2⋅sin(wt−α2)Theresultingcanbedescribedbythefollowlng:Y=A⋅sin(wt−α)withtheamplitudeA2=a12+a22+2a1a2⋅cosδ(1)andthephasedifferenceδ=α1−α2InaMichelsoninterferometer,thelightbeamissplitbyahalf-silveredglassplateintotwopartialbeams(amplitudesplitting),reflectedbytwomirrors,andagainbroughttointerferencebehindtheglassplate.Sinceonlylargeluminousspotscanexhibitcircularinterferencefringes,theIightbeamisexpandedbetweenthelaserandtheglassplatebyalensL.IfonereplacestherealmirrorM3withitsvirtualimageM3/,,Whichisformedbyreflectionbytheglassplate,apointPofthereallightsourceappearsasthepointsP/,andP"ofthevirtuallightsourcesLlandL2·Duetothedifferentlightpaths,usingthedesignationsinFig.2,图2thephasedifferenceisgivenby:δ=2πλ⋅2⋅d⋅cosθ（2）λisthewavelengthofthelaserljghtused.Accordingto(1),theintensitydistributionfora1=a2=aisI~A2=4⋅a2⋅cos2δ2(3)Maximathusoccurwhenδisequaltoamultipleof2π,hencewith(2)2⋅d⋅cosθ=m⋅λ；m=1，2，…..(4)i.e.therearecircularfringesforselected,fixedvaluesofm,andd,sinceθremainsconstant(seeFig.3).IfonealtersthepositionofthemovablemirrorM3(cf.Fig.1)suchthatd,e.g.,decreases,accordingto(4),theciroularfringediameterwouldalsodiminishsincemisindeeddefinedforthisring.Thus,aringdisappearseachtimedisreducedbyλ/2.Ford=0theciroularfringepatterndisappears.IfthesurfacesofmirrorsM4andM3arenotparallelinthesenseofFig.2,oneobtainscurvedfringes,whichgraduallychangeintostraightfringesatd=0.空气衍射系数的...
