qânun-e Snell (#)
Fr.: loi de Snell, loi de Descartes
The relationship between angles of incidence and refraction for a wave incident on an interface between two media with different indices of refraction. The law states that the ratio of the sine of the → angle of incidence to the sine of the → angle of refraction is a constant: n1/n2 = sinθ2/sinθ1. See also → refractive index. Also known as Descartes' law or the law of refraction.
Named after Dutch mathematician Willebrord Snellius (1580-1626), one of the discoverers of the law; → law.