Find the angle between the ray emergent ray and incident ray when the light goes from air to glass slab. Given μglass = 1.5
By using Snell's law at first surface,
μglass Sin x = μair Sin i
(Eq1): Sin x = Sin i μglassμair
This refracted ray will act as an incident ray for the second surface with incident angle equal to the angle of refraction.
Now using snell's law again at second surface,
μglass Sin x =Sin c μair
(Eq2): Sin x = Sin c μairμglass
From Eq1 and Eq2, we can say i = c
Both rays will be parallel to each other, hence, the angle between them will be zero.