Why does light ray incident on a rectangular glass slab emerges parallel to itself explain using a diagram?

Text Solution

Solution : In the given figure, EO is the incident ray, OO' is the refracted ray and O'H is the emergent ray. <br> <img src="https://d10lpgp6xz60nq.cloudfront.net/physics_images/ARH_NCERT_EXE_SCI_X_C10_S01_021_S01.png" width="80%"> <br> The extent of bending of the ray of light at the opposite parallel faces AB (air-glass interface) and CD (glass-air interface) of the rectangular glass slab is equal and opposite. This is why the ray emerges parallel to the incident ray on a rectangular glass slab. However, the light ray is shifted sideward slightly. When glass slab in immersed in any medium the interface AB (medium-glass) and CD glass medium are equal and apposite so, the emergent ray will always be parallel to the incident ray.