Willebrord Snell

Willebrord Snell , 1591-1626, Dutch mathematician. He is generally credited with the discovery (1621) of the law of the refraction of light. In 1613 he became professor of mathematics at the Univ. of Leiden. His two chief works are Eratosthenes Batavus (1617) and Cyclometricus (1621).

Snell's law The ratio of the sine of the angle of incidence (i) to the sine of the angle of refraction (r) is a constant for any two isotropic media bounded by a common interface. The refractive index n is given by: n = sini/sinr, and n₁sini = n₂sinr, where n₁ and n₂ are the refractive indices of the two media. The law also indicates that a P-wave incident upon a boundary will be reflected and refracted partly as a P-wave and partly as an S-wave. The law was formulated by the Dutch astronomer and mathematician Willebrord Snell (1591–1626).