# Refraction and Prisms

## Main Question or Discussion Point

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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mfb
Mentor
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.

Which triangle? If you mean the one formed by the refracted ray, it is not a right angle triangle.

blue_leaf77
Homework Helper
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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sophiecentaur