Question

Unpolarised beam of light of intensity $I$ is incident on two polarisers in contact. The angle between the axes of the two polarisers is $\theta$. Intensity of the light finally emerging from the combination is

• A. $I{\cos }^2\theta$
• B. $\left(\frac{I}{2}\right){\cos }^2\theta$
• C. $I{\cos }^4\theta$
• D. $\left(\frac{I}{2}\right)\cos \theta$

Answer 1

Answer: (B)

After first polarisation intensity becomes $\frac{I}{2}$
After second polarisation it is $\frac{I}{2}{\cos }^2\theta$ by law of malus.