Brewster's angle

Brewster's angle: For a plane electromagnetic wavefront[?] incident on a plane boundary between two dielectric media having different refractive indices, the angle of incidence at which transmittance[?] from one medium to the other is unity when the wavefront is linearly polarized with its electric vector parallel to the plane of incidence.

Note 1: Brewster's angle θ_B, is given by where n ₁ and n ₂ are the refractive indices of the respective media, and ε₁ and ε₂, their respective electric permittivities.

Note 2: For a randomly polarized ray incident at Brewster's angle, the reflected and refracted rays are at 90° with respect to one another.

Source: from Federal Standard 1037C