Brewster angle, θB

When an unpolarized planar electromagnetic wavefront impinges on a flat dielectric surface, there is a unique angle ( $θ B$ ), commonly referred to as Brewster angle, at which the reflected waves are all polarized into a single plane.

Notes:

Expression for Brewster angle:
$θ B = arctan ⁡ n 2 n 1 = arctan ⁡ ( ɛ 2 ɛ 1 ) 1/2$
where $n 2$ and $n 1$ are the refractive indices of the receiving surface and the initial medium, respectively, and $ɛ 2$ and $ɛ 1$ are the relative static permittivities (formerly called dielectric constants).
For a randomly polarized beam incident at Brewster angle, the electric fields of the reflected and refracted waves are perpendicular to each other
For a wave incident from air on water ( $n = 1.333$ ), glass ( $n = 1.515$ ), and diamond ( $n = 2.417$ ), the Brewster angles are $53$ , $57$ , and $67.5 degrees$ , respectively.

Source:

PAC, 2007, 79, 293 (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 310