428 Diffraction Patterns and Polarization*P38.67(a)Constructive interference of light of wavelength λon the screen is described by dmsinθλ=where tanθ=yLso sin=+yLy22. Then dyLymafej12+=−. Differentiating withrespect to ygivesdL ydyL yy mddydmddydLddymLy112023222222++−FHGIKJ=+−+==+−+=+−−bgafafafaf(b)Here sin=gives 1080001550 1029−−=×mmsin, =××FHGIKJ=°−−−sin..166055 101026 1m1.25myL°=tan.tan..240261118m mNow ddydLy=+=×+=−−2627125 10124118377 10377af...m 2.40 mmnm cm .P38.68For a diffraction grating, the locations of the principal maxima for wavelength are given bysin=≈mdyL. The grating spacing may be expressed as daN=where ais the width of the gratingand Nis the number of slits. Thus, the screen locations of the maxima become yNLma=. If twonearly equal wavelengths are present, the difference in the screen locations of corresponding
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