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See index of refraction.
(General Physics) physics a measure of the extent to which radiation is refracted on passing through the interface between two media. It is the ratio of the sine of the angle of incidence to the sine of the angle of refraction, which can be shown to be equal to the ratio of the phase speed in the first medium to that in the second. In the case of electromagnetic radiation, esp light, it is usual to give values of the absolute refractive index of a medium, that is for radiation entering the medium from free space. Symbol: ν or μ
in′dex of refrac′tion
a number indicating the speed of light in a given medium, usu. as the ratio of the speed of light in a vacuum or in air to that in the given medium.
n → Brechzahl f, → Brechungsindex m