Brewster's angle: a standalone construct

Brewster's angle is the particular angle of incidence at which light reflecting off a dielectric surface comes back completely polarised in the plane parallel to the surface, because at that angle the reflected and refracted rays are perpendicular and the component polarised in the plane of incidence is not reflected at all. David Brewster's 1815 On the laws which regulate the polarisation of light by reflexion from transparent bodies established that this angle is set by the refractive index, its tangent equalling the index ratio. The referent is the polarising angle of a surface, used in polarisers, laser Brewster windows, and index measurement, defined by the material's refractive index.[1]

Unit

The angle of incidence whose tangent equals the ratio of refractive indices

Recovery means

Not applicable

Measured by

Located as the incidence angle giving minimum (ideally zero) reflection for in-plane polarisation, from which refractive index can be inferred