Trace the course of a ray of ligth through a rectangular glass slab. From the plot discuss what happens when
(i) ray goes from a rarer to a denser medium ?
(ii) ray goes from a denser to a rarer medium?

Explanation

the course of rays through a rectangular glass slab ABCD.
Two refractions occur, one at Q and other at R. PQ is incident ray, travelling in air `i_(1)` is angle of incidence in air
QR is refracted ray, travelling in glass, `r_1` is angle of refraction, in glass.
For second refraction at R
QR is incident ray in glass `r_2` is angle of incidence in glass RS is refracted ray in air e is angle of emergence, in air.
(i) As `angle r_1 lt anglei_1` , therefore, when a ray goes from a rarer medium (air) to a denser medium (glass), the ray bends towards normal.
As `angle e gt angle r_2`, therefore, when a ray goes from a denser to a rarer medium, it bends away from normal.