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Law of Refraction

  1. Mar 5, 2006 #1
    This seems really easy but I am having a really hard time getting the correct answer to this question. Any help would be much appreciated.

    A ray in air is incident on a glass plate whose index of refraction is 1.60. The angle of refraction is one half the angle of reflection. The angle of refraction is closest to:

    I know to use snell's law and theta_a = theta_r but the problem doesn't give me any angles to compute theta_b

    (1) sin (theta_a) = 1.60 sin (theta_b)
    theta_b = 1/2 theta_r = 1/2 theta_a
    I'm I suppose to assume something here?
  2. jcsd
  3. Mar 5, 2006 #2


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    Well if you know [itex]\sin\theta_b = \frac{1}{2}\sin\theta_a[/itex], then all you need to do is a subsitution.
  4. Mar 5, 2006 #3
    Since [tex]\theta_b=(1/2) \theta_a[/tex] then
    Cancelling the sine terms:

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