Why does a light ray incident on a rectangular glass slab immersed in any medium emerges parallel to itself? Explain using a diagram.
When a ray of light enters from one rarer medium (say air) to another denser medium (say glass), it bends towards the normal. When the same ray of light exits from second medium into first medium, it bends away from the normal. In this case, the extent of bending of ray at opposite parallels (air-glass interface and glass-air interface) is same. Due to this, the emergent ray is parallel to incident ray.
