Question

A light ray passes from air through a thin rectangular plastic slab (refractive index = 1.3). If the ray in air makes an angle of ${45}^{\circ }$ with the normal after leaving the slab, what is the angle of incidence for the light falling on the plastic slab?

Answer 1

For a rectangular slab, there is no change in the direction of the emergent ray. It is only shifted a little sideways. So the angle of incidence is equal to the angle of emergence, i.e., ${45}^{\circ }$.