Brewsters law states that "The tangent of the angle of polarisation for a given medium is numerically equal to the refractive index of the medium".
The angle of incidence at which the reflected light from a transparent surface is completely plane polarised is called polarising angle(Brewster's angle).
i e tan i = n
Where 'i' is the polarising angle and 'n' the refractive index of the material of the reflecting surface.
He also found out that at the polarising angle , the reflected and refracted rays are perpendicular to each other.
Brewster window is an application of Brewster's law and Brewster's angle.It is a glass window which transmits 100% of light.Brewster's windows are used in gas lasers and in solid state lasers.In solid state lasers,the ends of the laser medium is cut at brewster's angle to make a Brewster window.
Polarized sunglasses use the principle of Brewster's angle to reduce glare from the sun reflecting off horizontal surfaces such as water or road.