Snell' Law of Refraction: How Light Rays Are Refracted in the Medium

Snell's law of refraction describes the behavior of light rays when passing from an optically denser medium into an optically less dense medium (or vice versa), such as from air into glass or from water into air.

If a ray of light enters a medium (e.g. water) with the refractive index \(n_1\) at the angle \(\alpha_1\) (between the perpendicular and the incident ray) from the medium (e.g. air), the angle of refraction \(\alpha_2\) (between the perpendicular and the incident ray) is determined by Snell' law of refraction: