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Homework Help: Diffraction grating

  1. Jul 20, 2008 #1
    1. The problem statement, all variables and given/known data

    A laser is used to illuminate a diffraction grating that has spacing of 637 lines per mm. The grating sits 11.6 cm in front of a screen. Find the distance to the first and second maxima (y1 and y2) for the laser wavelength of 643 nm. Express your answers in mm.

    2. Relevant equations

    wavelength = (s/m)(ym/sqrt(L2+ym2))

    3. The attempt at a solution

    s = 1/637 = .00156 mm
    L = 116 mm
    wavelength = 643 X 10-6 mm

    I tried solving this equation for ym, but the answer I got was wrong. Is there another way to do this problem?
  2. jcsd
  3. Jul 20, 2008 #2


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    Homework Helper

    Hi cyclonefb3,

    What answers did you get?
  4. Jul 20, 2008 #3
    I got 116 mm for both.
  5. Jul 20, 2008 #4


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    Homework Helper

    Can you show the details of how you got those two answers (what numbers you used and so forth)? I'm not getting that from your equation.
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