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Homework Help: Slit diffraction in water?

  1. May 13, 2005 #1
    slit diffraction in water???

    Hello! I'm having trouble answer this hw problem:

    Suppose the entire apparatus (light of wavelength X nm from a distant source is incident on a slit Y mm wide, and the resulting diffraction pattern is observed on a screen Z m away) is immersed in water (n=1.33).

    Then what is the distance between the two dark fringes on either side of the central bright fringe?

    I know what I want to use the equation for Dark fringes in single-slit diffraction:
    sin(theta) = m*lamda/a

    in my case, m = 1
    and a = y

    I'm not sure how to solve this problem now that the entire apparatus is immersed in water? I know water affects this, but how? Can you help me start this problem?
  2. jcsd
  3. May 13, 2005 #2

    Doc Al

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    Staff: Mentor

    How does the wavelength of light depend on the index of refraction of the medium?
  4. May 13, 2005 #3
    thanks! i knew it was a concept I had studied a few chaptes earlier but it completely slipped my mind. that's right, index of refraction depends on c and hte speed of light in that particular medium!! =)
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