Question

When an unpolarized light of intensity $I_0$ is incident on a polarizing sheet, the intensity of the light which does not get transmitted, is :

• A. zero
• B. $I_0$
• C. $\frac{I_0}{2}$
• D. $\frac{I_0}{4}$

Answer 1

The correct option is C $\frac{I_0}{2}$

Since the incident light is unpolarized, the intensity of transmitted light at an angle $\theta$ with respect to the polarizing axis is: $I=I_0{\cos }^2\theta$
Integrating over all angles between $0^0$ and ${360}^0$ is $I_0({\cos }^2\theta {)}_{avg}=\frac{I_0}{2}$
Hence, the intensity of light not transmitted is $I_0-\frac{I_0}{2}=\frac{I_0}{2}$