Question

What is the relation between angle of incidence i and angle of refraction r in the glass ?

Answer 1

From snell's law

Snell's law (also known as the snell-descartes law and the law of refraction) is a formula used to describe the relationship between the angle of incidence and refraction, when referring to light or other waves passing through a boundary between two different isotropic media, such as water, glass, or air.

$refractiveindex=\frac{sini}{sinr}\mu =\frac{sini}{sinr}$