Translations:Snell's law/3/en

where i is the angle of the incident wave, V_i is the velocity of the incident medium, r is the angle of refraction, and V₂ is the velocity of the second medium. If sinr exceeds 1 as given by this equation, a head wave will be generated. Snell's law is also called Descartes' law. In anisotropic media (where wavefronts are not necessarily perpendicular to raypaths), Snell's law holds for the angles measured between an interface and the wavefronts, using phase velocities. The law is named for Willebrord Snellius (1580-1626), Dutch mathematician.