Brewsters angle

When light moves between two media of differing refractive index, light which is p-polarised with respect to the interface will not be reflected from the interface at one particular incident angle, known as Brewster's angle.

It may be calculated by:

θ_B = arctan( n₂ / n₁ ) ,

where n₁ and n₂ are the refractive indices of the two media.

Note that, since all p-polarised light is refracted, any light reflected from the interface at this angle must be s-polarised. A glass plate placed at Brewster's angle in a light beam can thus be used as a polariser.

See also Fresnel equations.