Question

why does a light Ray incident on a rectangular glass slab immersed in any medium emerges parallel to itself ?​

Answer 1

“A ray of light incident on a rectangular glass slab immersed in any medium emerges parallel to itself”. ... - Hint:When a ray of light enters the medium having higher refractive index, it bends towards the normal and when emerges out to the same medium as before, it gets refracted away from the normal.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. However, the light ray is shifted sideward slightly