Snell’s Law describes the relationship between the angle of
incidence and the angle of refraction when refraction occurs.
Mathematically, Snells’s Law is written as:
n1 Sin α1 = n2 Sin α2
where n1 = index of refraction of medium-one (incident ray)
n2 = index of refraction of medium-two (refracted ray)
α1 = angle of incidence
α2 = angle of refraction