## The Brewster Angle

Polarisation to some degree occurs whenever light is reflected from a non – conductor of electricity. The degree of polarisation depends on the surface and angle of incidence.

For a particular anglethe beam is completely plane polarised as shown below.is known as the polarising angle or Brewster angle.

In fact for a material of refractive index n, the Brewster angle p is give by(1)

It is easily shown that the refracted and reflected beams are at right angles.

From Snell's law we getSubstituting forfrom (1) we get

Nowsohenceand similarly

Nowhence