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Homework Help: Dispersion and Prisms

  1. May 17, 2004 #1
    I'm confused on this question. I would show my work, but I'm not sure on how to even approach the question. The book labels this problem as straight forward, but I still don't see it and I'm confused on which formula(s) to use..

    A narrow white light beam is incident on a block of fused quartz at an angle of 30.0 deg. Find the angular width of the light beam inside the quartz.

    I tried to use Snell's law, but don't see how. My book shows no specific formulas under the dispersion and prisms section.

    Any help is greatly appreciated.

  2. jcsd
  3. May 18, 2004 #2


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    You assume that by "white light", it means that the beam contains the range of frequency/wavelength of the visible light in the ordinary spectrum. So look up the longest and shortest wavelength in the visible light spectrum.

    Next, use Snell's law and find the diffraction angle for both those wavelengths. This will be the maximum and minimum diffraction angles made by the white light. This then is the angular width of the beam inside the prisim.

  4. May 18, 2004 #3
    Okay, I understand it now. The white light is where I was getting confused..

    Thanks for the help! :smile:
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