Question

3a. Light traveling in air encounters a flat side of a solid block of a transparent material that is completely immersed in air, i.e., it is completely surrounded by the air. Some of the incident light is reflected back into the air and some enters the material. If the angle of incidence that the light makes at the flat side is 16.8 degrees, what is the angle that the light is reflected back into the air relative to a perpendicular to the surface? Give your answer in the form "ab.c" degrees.

Answer 1

a) Well since it is been asked about the angle for the reflected light that was incident upon the block thus from the law of reflection it will same as the angle of the incident light and thus the elected light will be same as 16.8 degrees w.r.t normal to surface.

c) Now for the refracted light to be totally internally reflected about the second surface, we have snell's law stating

n₁sini = n₂sinr

For the minimum angle; sinr = 1 now since the other medium is air n₂ = 1

sin i = 1/n₁

Given n₁ = 2.02

sin i =1/2.02 = 0.495

=> i = 29.7^o

This will be the minimum angle at which the refracted ray must incident upon the second surface.