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 = sin i/sin r, and n1sin i = n2sin r, 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).
Subjects: Earth Sciences and Geography.