402 Interference of Light WavesP37.60Bright fringes occur when212tnm=+FHGIKJλand dark fringes occur when2tnm=FHGIKJ.The thickness of the film at xisthx=FHGIKJA.Therefore, xhnmbrightFHGIKJA212and xmhndark=A2.FIG. P37.60P37.61Call tthe thickness of the film. The central maximumcorresponds to zero phase difference. Thus, the addeddistance ∆rtraveled by the light from the lower slit mustintroduce a phase difference equal to that introduced bythe plastic film. The phase difference φisφπ=FHGIKJ−21tnaaf.The corresponding difference in path length∆ris∆rtntnaaa=FHGIKJ=FHGIKJ−FHGIKJ=−π221.Screenθy'Zeroorderm= 0LThinfilmα∆rdFIG. P37.61Note that the wavelength of the light does not appear in this equation. In the figure, the two raysfrom the slits are essentially parallel.Thus the angle may be expressed astan==′∆rdyL.Eliminating ∆rby substitution,′=−yLtnd1gives
This is the end of the preview. Sign up
access the rest of the document.
This note was uploaded on 12/14/2011 for the course PHY 203 taught by Professor Staff during the Fall '11 term at Indiana State University .