(N/A) The ray diagram shows the path of a light ray passing through a rectangular glass slab. When a light ray enters the glass slab from air,it bends towards the normal because it travels from a rarer medium to a denser medium. Upon emerging from the glass slab into the air,it bends away from the normal.
$1$. Angle of incidence $(i)$: The angle between the incident ray and the normal at the point of incidence.
$2$. Angle of refraction $(r)$: The angle between the refracted ray and the normal inside the glass slab.
$3$. Angle of emergence $(e)$: The angle between the emergent ray and the normal at the second surface.
$4$. Lateral displacement: The perpendicular distance between the original path of the incident ray and the emergent ray.
The refractive index $(n)$ of the glass slab with respect to air is given by Snell's Law at the first interface:
$n = \frac{\sin i}{\sin r}$