Reflection is governed by the equation Ði = Ðr¢  and refraction by the
Snell’s law, sini/sinr = n, where the incident ray, reflected ray, refracted
ray and normal lie in the same plane Angles of incidence, reflection
and refraction are i, r ¢ and r, respectively 2 The critical angle of incidence ic for a ray incident from a denser to rarer
medium, is that angle for which the angle of refraction is 90°