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Diffraction Grating lab

  1. May 7, 2008 #1
    You find two unlabelled diffraction gratings in your lab. From purchase records, you know that one grating has 5000 lines/cm, while the other has 10 000 lines/cm. Given the following equipment, describe how you would determine which is the grating with 10 000 lines/cm:
    • Red laser
    • detection screen
    • the two unknown diffraction gratings
    describe what difference you would observe.
    n = d sin(theta)
    d=1/5*105 = 2*10-6
    d=1/1*106= 10-6
    I don’t know how to start can someone give me any idea about this question
  2. jcsd
  3. May 7, 2008 #2
    At what angle would you see the first maximum for the 5000 line grating? At what angle would you see the first maximum for the 10000 line grating?

    If you had a screen, say, 10 m away from the 5000 line grating, how far would the central maximum be from the first, second and nth maximas? What about for the 10000 line grating?
  4. May 7, 2008 #3
    You missed a [tex]\lambda[/tex] in your equation. It should read

    [tex] n \lambda = d sin(\theta) [/tex]

    Anyway, what do you expect the difference between the interference patterns to be when you shine the laser on the two different gratings? Where is the first order (n=1) maximum with each grating?

    And I see oedipa maas just posted similar remarks. . .
    Last edited: May 7, 2008
  5. May 11, 2008 #4
    thats what i got
    suppose the wavelength= 1cm = 1*10^-9
    and m= 1
    when d= 2*10^-6 m/line
    theta= 0.029

    when d= 10^-6
    theta= 0.057
    that's all what i got
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