# When Light Travels from an Optically Denser Medium to a Rarer Medium, Why Does the Critical Angle of Incidence Depend on the Colour of Light? - Physics

Short Note

When light travels from an optically denser medium to a rarer medium, why does the critical angle of incidence depend on the colour of light?

#### Solution

The critical angle for a given pair of medium is given by

Sin "i"_"c" = (1)/mu

where μ is the refractive index of the denser medium. The refractive index of a medium depends on the wavelength by the relation

mu = "A" + "B"/lambda^2

and each colour of light is associated with a specific wavelength, so as the wavelength of light increases critical angle increases.

Concept: Rarer and Denser Medium
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