Question

Unpolarized light with intensity I0 strikes a perfect polarizer. What is the intensity of light that makes it through the polarizer? Select one: a. 1/2 I0 b. 0 c. 1/4 I0 d. It depends on the orientation of the polarizer e. I0

Answer 1

As per law of Malus if a plane polarized light, with angle of vibration of electric field with the polarizing direction of polarizer being ϴ, is incident on the polarizer then intensity of light coming out of polarizer is given by

                                                                          I = I₀ cos²ϴ

But for un polarized light since ϴ varies randomly and hence we need to take the average value of cos²ϴ which is ½. So intensity of light coming out of the polarizer is

                                                                          I = I₀/2

The correct option is, a.