Brewster's Angle Calculator

About this calculator

Brewster's angle is the specific angle of incidence at which light reflecting off a surface becomes completely polarized perpendicular to the plane of incidence, calculated as θ_B = atan(n₂/n₁), where n₁ and n₂ are the refractive indices of the first and second media. At this angle, derived from the Fresnel equations, the reflected and refracted rays end up exactly 90° apart, which is why the parallel-polarized component of reflected light drops to zero.

Optics engineers use Brewster's angle to design polarizers, laser windows, and anti-reflective components (Brewster windows in laser cavities minimize reflection loss for one polarization), photographers and cinematographers rely on the same physics — often intuitively — when using polarizing filters to cut glare off water or glass at the right angle, and physics students use it as a core application of Fresnel reflection and polarization theory.