Explain the lateral shift for the refraction of light through a rectangular glass slab.

(N/A) When a light ray passes through a rectangular glass slab,refraction occurs at two parallel interfaces: air-glass and glass-air.
$1$. At the first interface (air-glass),the light ray bends towards the normal as it enters the denser medium.
$2$. At the second interface (glass-air),the light ray bends away from the normal as it enters the rarer medium.
$3$. According to Snell's law,the angle of incidence at the first surface $(i_1)$ is equal to the angle of emergence at the second surface ($e$ or $r_2$ in the diagram). Thus,the emergent ray is parallel to the incident ray.
$4$. Although the direction of the light ray remains unchanged,it undergoes a perpendicular displacement from its original path. This perpendicular distance between the path of the incident ray and the emergent ray is known as the lateral shift or lateral displacement.