A light strikes the boundary of a medium at a 45 degree angle. Instead of entering the second medium, the light reflects back into the first medium. What can you conclude about the index of refraction of the second medium?

A it is much smaller than the index of refraction of the first medium

B It must equal to zero

C It is much larger than the index of refraction of the first medium

D It must be equal to 1.00

D It must be equal to 1.00

Explanation:

The refraction in the second medium must be equal to 1. The refraction index is given as the ration of the angle of incidence to the angle of refraction. This is given as a fraction. In other words:

where Θ₁ and Θ₂ are angles of incidence an refraction, and n is the refractive index.

At a critical angle, the refraction is equal to the reflection inside the medium. This results in a phenomenon called total internal reflection where light is reflected internally in the medium.

it is the most commonly accepted one