Question

A ray of light is travelling through a rectangular glass slab (refractive index \(\frac{3}{2}\)) and is incident on the horizontal glass-air surface at the critical angle for the two media. The slab is then brought in contact with water (refractive index \(\frac{4}{3}\)) such that a thin horizontal layer of water is formed on the surface of the slab. Find the angle at which the ray will emerge into air from the water-air surface.

Hint:

For parallel layer media arrangements, intermediate layers do not alter the final output angle relations between the first and last boundaries. Since the light entered at the critical angle for glass-air, it will exit at \(90^{\circ}\) into the air, regardless of what intermediate layers like water are added in between.

Answer 1