what is polarising angle? what is the realation between polarising angle and critical angle?

When the unpolarized light incident on the interface of two different medium (with two different refractive index n₁ and n₂) at an perticular angle such that reflected and refracted light are polarized and the angle between reflected and refracted light is 90°, this perticular angle is called polarising angle. It is also known as Brewster's angle θ_B.

 

when unpolarized light incident on a boundary at polarizing angle θ_B, the reflected light consists only of components perpendicular to the plane of incidence  and refracted light consists only of components parallal to the plane of incidence.

 

θ_{B = tan^-1} (n2/n1)