When light reflects from a non-metalic surface, the reflected light will be polarized in the plane of the surface. The degree of polarization depends on the angle the light hits and the refractive indexes of the air and refractive medium. The angle of maximum polarization is called BREWSTER'S ANGLE and is satisfied by:

where n2 is the index of refraction of (say) glass and n1 is the index of refraction of (say) air. Tha angle between the refracted and reflected rays is 90 at Brewster's angle.

Polarized Light Island
Polaroid Island (Audry's)
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