Refractive index

The refractive index of a medium is the ratio of the speed of light in a vacuum to the speed of light through the medium.

The speed of light through a vacuum is 300,000,000 m/s

Hence the speed of light through glass that has a refractive index of 1.5 is

3 x 108 ÷ 1.5 = 2 x 108 m/s

Material
Refractive index
glass
1.5
water
1.33
turpentine
1.47
perspex
1.49
diamond
2.4

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Date Last Modified: April 2003

Emanuel School, London SW11 1HS

All text and diagrams copyright of J.C.Naylor