Light waves are not longitudinal but are transverse

The wave emerge according the direction of slit

Source of light

slit

Ordinary Unpolarised light

Polarized light

In an ordinary light the vibrations of the electric vector occur in all possible direction in the plane perpendicular to the direction of wave. The wave emerge from the crystal which are parallel to its axis.

Tourmaline Crystal

This phenomenon is called ‘Polarization of light’

Polarization of light

Two plane-Polarized waves of equal amplitude and at right angles to each other are moving in the z direction. They differ in phase by 900; where one has maximum values, the other is zero.

X

Y

Z

Polarization of Light by Reflection

Normal

ip ip

r

Air

Glass

Polarize

d LightUnpolarised Light

Brewster’s Law

For a particular angle of incidence, the reflected light is completely plane-polarized with vibrations perpendicular to the plane of incidence. The angle of incidence is called the ‘Angle of Polarization’ ip.

µ = tan ip (Brewster’s Law)