diffraction.ppt

urwheneverawavepassesthroughanaperture(缝隙),x-raydiffraction,andholography(全息照相).diffraction(衍射)alternatingbrightanddarkfringes(明暗交替的条纹)aperture(孔,缝隙)infinitesimal(无穷小的)emanate(发出,发射)Fresneldiffraction(菲涅尔衍射)Fraunhoferdiffraction(夫琅和费衍射)diffractiongrating(衍射光栅)holography(全息摄影术)KeyTerms:HuygensprincipleSingleslitgratingX-raydiffractionTypeofdiffractionphenomenadiffractionoflightphenomenaruleapplication“thebendingoflightaroundanobstacle”31-1DiffractionPhenomenalightsourceobstaclescreen*S*SscreenobstaclescreenobstacleWhatisthedifferencebetweeninterferenceanddiffraction??Fresnel:finitedistanceinfinitedistancefinitedistancefinitedistanceinfinitedistancefinitedistanceFraunhofer:infinitedistanceinfinitedistance31-2FresnelandFraunhoferDiffractionfOPAaBC*-3FraunhoferDiffractionfromaSingleSlit222ABa()(asin)intoseveralshortsegmentsofequallength/2,/2,=asin=2(/2),:howabout4,6,8…strips?howabout3,5,7…strips?Caution:1)k0;2)strips?3)?;parewithYoung’s…;22ABaCWidthofthesingle-slitpatternAngularspreadoftheCentralbrightbands:afIUsesmallangleapproximation:sin;tgWidthofthecentralbrightbands:Widthofthesidebrightbands: