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Distance between two second order maxima

  1. Sep 29, 2009 #1
    1. The problem statement, all variables and given/known data
    Monochromatic light strikes a diffraction grating at normal incidence before illuminating a screen 1.99 m away. If the first-order maxima are separated by 1.36 m on the screen, what is the distance between the two second-order maxima?


    2. Relevant equations
    I think these are the relevant equations:
    deltaL = dsinθ
    y = Ltanθ


    3. The attempt at a solution
    L = 1.99 m
    I'm not sure where the 1.36 and 1.99 come in.
     
  2. jcsd
  3. Sep 29, 2009 #2

    Delphi51

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    Homework Helper

  4. Sep 29, 2009 #3
    So I only need the d sinθ = mλ equation?
    Would you be able to help walk me through it?
    I feel like I need the y = Ltanθ or deltaL = dsinθ equation.
    Doesn't L = 1.36 for the first order maxima?
    d = 1.99 m
    m = 2?
     
  5. Sep 29, 2009 #4

    Delphi51

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    Homework Helper

    Draw the triangle with theta, x (distance from center to maximum - half the 1.36), L (L is the hypotenuse), and the 1.99 m distance to the screen. Use the triangle and some trig to find theta.

    Use the formula to find lambda/d. This value doesn't change as you move to 2nd order, so you can use the formula again with this value to find theta when m = 2.
     
  6. Sep 30, 2009 #5
    Thanks!
     
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