The sine of the angle of incidence bears a constant ratio with the sine of the angle of refraction for a given pair of media. This law is also known as the Snell's law, named after Willebrord Snell.
The ratio sin i / sin r gives the refractive index for a a given pair of media.
Refractive Index = sin i / sin r = speed of light in medium 1 / speed of light in medium 2
If medium 1 is vacuum, the ratio c1/c2 is defined as the absolute refractive index of medium 2, and is denoted by 'μ' (mew).
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