Question

In case of refraction of light through a rectangular glass slab, explain why (a) the emergent ray is parallel to the direction of the incident ray (b) the emergent ray is shifted sideward slightly?

Answer 1

(a)
* In the case of rectangular slab, the light ray undergoes refraction two times at opposite faces.
* At first refracting face, the light rays enters glass from air so that it bends towards the normal, whereas at the second refracting face, the light ray bends away from the normal where it enters air from glass.
* As the light ray undergoes refraction two times in opposite directions, the emergent ray is parallel to the incident ray.

(b0
As the light ray travels some distance at some angle inclined to the face of the slab, there is some lateral displacement takes place in the slab. So, the emergent ray is slightly shifted sideward.