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Homework Help: Index of refraction of an optical fiber

  1. Feb 14, 2009 #1
    1. The problem statement, all variables and given/known data
    The glass core of an optical fiber has an index of refraction 1.62. The index of refraction of the cladding is 1.47.
    What is the maximum angle a light ray can make with the wall of the core if it is to remain inside the fiber?

    2. Relevant equations

    theta = sin ^-1 (n2/n1)

    3. The attempt at a solution
    i used the equation and got angel 65.15 which was wrong
  2. jcsd
  3. Feb 15, 2009 #2


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    Homework Helper

    The critical angle is 65 all right, but that is the angle of incidence - measured from a line perpendicular to the surface. The question asks for the angle "with the wall of the core". So you want 90-65.15.
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