Question

A ray from air enters water, then through a thick layer of Glass placed below water. After passing through glass, it again comes out in the air medium. Then final emergent ray will
(a) Bend towards the normal
(b) Bend away from the normal
(c) Suffer lateral displacement
(d) Have the same path add if it had not passed through glass and water

Answer 1

Light rays are reversible. They travels exactly the same path if they are going in the opposite direction. So if light is refracted some angle going from,say,air to glass,it would refract exactly in the same angle in the opposite direction going from glad to air.

The bottom side of the slab is the reversed situation of going from glass to air.

If the two sides of glass slab are parallel,then no new angles are introduced. The two refraction cancel out the change in direction of the ray.But as you can see the emergent ray is displaced laterally, although it's parallel to the incident Ray.