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Diffraction Gratings

  1. Apr 19, 2013 #1
    1. The problem statement, all variables and given/known data

    A grating places a spectral line of wavelength 681 nm at 12 degrees in first order. At what angle is a line of wavelength 439 nm observed in second order?

    2. Relevant equations

    I believe dsinθ= mλ

    3. The attempt at a solution

    This is where I get lost, I can solve for every problem in difraction ( We did Rayleigh's criterion, double slit / single slit difraction) but I can't seem to be able to start a problem that involves grating, any pointers on how to start would be nice ^^ I just want to know how to approach the problem! :)
  2. jcsd
  3. Apr 19, 2013 #2


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    As far as finding the angles for the bright fringes, there is no difference between a grating and a double slit.

    One approach to this problem would be to use the information about the 681 nm line to determine the distance d between two slits in the grating.
  4. Apr 19, 2013 #3
    Ah, it worked. Thanks a lot ^^ Just a little question, if you don't mind answering it of course. If ever it asked me to look for the distance between the two waves, would I need to compare the equations or something?
  5. Apr 19, 2013 #4


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    I'm not sure what you mean by "distance between the two waves". Can you clarify that?
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