CBSE Class 12 · 2010 · Wave OpticsVery Short Answer

$\text{Unpolarized light:}$ light in which the electric field vibrates with equal probability in all directions in the plane perpendicular to the direction of propagation.
$\text{Polarization by reflection:}$ when unpolarized light is incident on a transparent surface, the reflected and refracted components are partially polarized. At a particular angle of incidence, the polarising angle $i_B$, the reflected ray is completely plane polarized with vibrations parallel to the reflecting surface (perpendicular to the plane of incidence); at this angle the reflected and refracted rays are mutually perpendicular.
$\text{Brewster’s relation:}$

where $\mu$ is the refractive index of the denser medium with respect to the rarer medium.