What is lateral shift?

(N/A) Lateral shift is defined as the perpendicular distance between the incident ray and the emergent ray when light passes through a parallel-sided glass slab.
When a light ray enters a glass slab,it undergoes refraction at the first surface and bends towards the normal.
At the second surface,it undergoes refraction again and bends away from the normal.
Due to these two refractions,the emergent ray is parallel to the incident ray but is laterally displaced.
The magnitude of the lateral shift $(s)$ is given by the formula: $s = \frac{t \sin(i - r)}{\cos(r)}$,where $t$ is the thickness of the slab,$i$ is the angle of incidence,and $r$ is the angle of refraction.