Brewster's Angle

Brewster's Law: When light strikes a transparent medium at the Brewster angle θ_B, the reflected ray is completely polarized with E perpendicular to the plane of incidence (s-polarization).

Brewster's law: tan θ_B = n₂/n₁. For light going from air (n=1) to glass (n=1.5): θ_B ≈ 56.3°.

At θ_B, the reflected and refracted rays are perpendicular to each other: θ_B + θ_t = 90°.

Only the s-component reflects; the p-component (E in the plane of incidence) is transmitted 100% into the denser medium.

Brewster's law is used to make polarizers (Brewster pile-of-plates) and in laser-tube end-windows to minimize reflection loss for one polarization.

Polarized sunglasses block horizontally polarized glare from horizontal surfaces (water, roads) reflected near the Brewster angle.

Reflected intensity at general angles is given by Fresnel equations; the p-component goes to zero exactly at θ_B.