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Homework Help: A Very Light Problem

  1. Jun 15, 2003 #1
    This question really has me stumped..i would appreciate it if anyone could help me out

    White light containing wavelengths of 400nm to 750 nm is shone normally onto a diffraction grating of 3000 lines/cm. Calculate the width of the spectrum that appears as the second antinode on a screen that is 100 cm away.

    Is there a specific formula I can use to solve the question? If so then please help.. thanks:smile:
  2. jcsd
  3. Jun 17, 2003 #2

    Tom Mattson

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    Staff Emeritus
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    Gold Member

    The condition for maxima/minima is the same as that of a 2-slit apparatus. For adjacent slits separated by a distance d, we must have:

    dsinθ=mλ for maxima and
    dsinθ=(m+1/2)λ for minima.

    In both cases, m is an integer.

    You use the information given about the grating to determine d and you use geometry to determine the displacement y of the antinodes on the screen. Note that your expression for y will depend on the wavelength λ.
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