Question

Find the final intensity of light $(I'')$, if the angle between the axes of two polaroids is $60^{\circ}$.

• A. $\frac{3I_{0}}{2}$
• B. $\frac{I_{0}}{2}$
• C. $\frac{I_{0}}{4}$
• D. $\frac{I_{0}}{8}$

Answer 1

Answer: (D)

From the first polaroid
$I' = \frac{I_{0}}{2}$
From second polaroid
$ I" = I' cos^{2} \theta = \frac{I_{0}}{2} cos^{2} \left(60^{\circ}\right) $
$= \frac{I_{0}}{2} \times\left(\frac{1}{2}\right)^{^2} = \frac{I_{0}}{8}$