Why does a light ray incident on a rectangular glass slab immersed in any medium emerge parallel to itself? Explain using a diagram.
Explanation:-
When a light ray enters a denser medium from a rarer medium it bends towards the normal.
Again, when this ray exists in the second medium and enters the first, it ends away from the normal. In this case extent of bending of the ray at opposite faces is the same, this is the reason why the emergent ray is parallel to the incident ray.