Question

A beam of unpolarized light of intensity \(I_0\) 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:

(1) \(\frac{I_0}{16}\)

(2) \(\frac{I_0}4\)

(3) \(\frac{I_0}2\)

(4) \(\frac{I_0}{32}\)

Answer 1

Correct option is (1) \(\frac{I_0}{16}\)

\(I_1 = \frac{I_0}2\)

\(I_B = (I_1) \cos^2 60^\circ\)

\(= \frac{I_0}2 (\frac 12)^2 \)

\(= \frac{I_0}8\)

\(I_C = I_B \cos^2 45^\circ\)

\(= \frac{I_0} 8 \times \left(\frac 1{\sqrt 2}\right)^2\)

\(= \frac{I_0}{16}\)