Question

A beam of partially polarized light can be considered to be a mixture of polarized and unpolarized light. Suppose we send such a beam through a polarizing filter and then rotate the filter through 360° while keeping it perpendicular to the beam. If the transmitted intensity varies by a factor of 4.8 during the rotation, what fraction of the intensity of the original beam is associated with the beam's polarized light?

Answer 1

Let the intensities of the unpolarized light and polarized light be 1 and a respectively.

After going through the polarizing ?lter the intensity of the unpolarized light will be 0.5 and the intensity of the polarized light will have a value between 0 and a.

{Maximum intensity of beam)/(minimum intensity of beam)

= (0.5 + a)/(0.5) = 4.8

Solving the equation gives a = 1.9

Fraction of the intensity of the original beam is associated with the beam's polarized light

= a/(1 + a) = 1.9/(1 + 1.9) = 0.655