Lesson: Chapter 5 — Optics

5.3.2. Total internal reflection and the critical angle 3 of 5 Reset answers

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Question 3

The critical angle of glass is 42°. A ray inside glass meets the surface at 45°. What happens?

A It is totally internally reflected B It is absorbed C It runs along the surface D It refracts out into the air

The right answer is the one marked above.

It is totally internally reflected. 45° is greater than the critical angle, 42° — which is how a 45° prism turns light.

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