Explain refraction through a parallel-sided glass slab.

Explanation:

1. Glass is a denser medium while the surrounding medium usually air is lighter.
2. When the light passes through the 1 interface of air-glass it bends towards the normal.
3. The angle of refraction for 1 st interface is equal to the angle of incidence for the second interface since both sides are parallel.
4. Using Snell's law the final angle of emergence becomes equal to the angle of incidence.
5. Hence the emergent ray is parallel to the incident ray.
6. There is a lateral displacement in the path of light.

The below-given diagram shows Refraction through the glass slab here $i=e=30°$