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Refraction and Prisms

  1. Sep 6, 2015 #1

    That is a page from my textbook. The book mentions that the angle of incidence on the right side when added with the angle of the refraction equals 60 degrees. Why is that?
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  3. Sep 6, 2015 #2


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    Consider the triangle formed by the light ray in the prism and the two prism borders. The sum of the interior angles is 180°, and one angle is 60°. Everything else follows from geometry with the right angles there.
  4. Sep 6, 2015 #3
    Which triangle? If you mean the one formed by the refracted ray, it is not a right angle triangle.
  5. Sep 7, 2015 #4


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    Triangle ABC:
    \angle A + \angle B + \angle C = 180^0
    Or triangle formed by B, C, and the prism's apex.

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    Last edited: Sep 7, 2015
  6. Sep 7, 2015 #5


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    Another way to look at it. The very top triangle has one angle of 60°. The other two angles are 90- i and 90-r etc. etc.....
  7. Sep 7, 2015 #6


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    That is the triangle I meant.
    And the sum of those three angles is 180 degrees.
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