Question

A beam of unpolarized light of intensity I0 is passed through a polaroid A, then through another polaroid B, oriented at 60º and finally through another polaroid C, oriented at 45º relative to B as shown. The intensity of emergent light is:

• A. $\frac{I_0}{16}$
• B. $\frac{I_0}{4}$
• C. $\frac{I_0}{2}$
• D. $\frac{I_0}{32}$

Answer 1

Answer: (A)

$\frac{I_0}{16}$

Answer 2

After the first polarizer : $I_1 = \frac{I_0}{2}$

After the second polarizer : $I_2 = I_1 \cos^2 60^\circ = \frac{I_0}{2} \times \frac{1}{4} = \frac{I_0}{8}$

After the third polarizer : $I_3 = I_2 \cos^2 45^\circ = \frac{I_0}{8} \times \frac{1}{2} = \frac{I_0}{16}$