Polarization Formula


Polarization Formula

The electromagnetic wave is characterized by its wave phase, frequency, and direction of propagation of transverse field oscillation which consists of transverse electric and magnetic components. The plane that uses the transverse electric vector is associated with a quantity known as polarization plane.  Light is a transverse electromagnetic wave, but any natural light can be considered as unpolarized since the propagation of all the planes are equally probable. Therefore, based on the position of the polarizer we get horizontal or vertical polarized light.Polarized light is a condition where when each light waves are placed parallel to each other. It is possible to polarize only transverse waves and that light is built up by transverse waves.  

The degree of polarization completely depends on the matter and the angle at which the light is reflected. All the substances that could polarize light are known as polarizer and the phenomenon is known as polarization.

Polarization angle or Brewster’s angle formula is given by:

tanθ = n2 / n1


n1 = initial medium

n2 = other medium.

I = Io cos2θ


Example 1

Determine the value of polarizing light angles when the refractive index of green color glass is 1.515 and that of violet color is 1.521.



n1 = 1.55

n2 = 1.52

The in1 = tan -1 (1.515 )

       = 56o 57’

The in2 = tan -1 (1.521 )

        = 56o 68’


Example 2

A plane polarized light beam is passed through an analyzer and the intensity is measured at 0.075 of the desired initial value. Identify the angle.



I = 0.075

We know that,

I = Iocos2θ  or cos2θ = I / Io = 0.075

Therefore, θ = 74.1


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