Answer to Question #95471 in Optics for Kikelomo

Question

A light beam undergoes total internal reflection at the interface between medium A, in which it propagates, and medium B, on the other side of the interface. Which medium has the greater index of refraction? Explain.

Answer 1

total internal reflection can occur in medium with a lower wave velocity than the second ("external") medium.

Refractive index is inversely proportional to wave velocity.

Therefore, medium A ("internal") has greater index of refraction, compared to the index of refraction in the medium B.