Question

Two polaroids are crossed. lfnow one of them is rotated through 30${}^{\circ }$ and unpolarised light of intensity $I_0$ is incident on the first polaroid, then the intensity of transmitted light will be

• A. $\frac{I_0}{4}$
• B. $\frac{3I_0}{4}$
• C. $\frac{3I_0}{8}$
• D. $\frac{I_0}{8}$

Answer 1

Answer: (D)

Intensity through first polaroid, $I_1=\frac{I_0}{2}$
$\therefore$ Intensity of transmitted light, $I=I_{1}co{s}^2\theta$
$=\frac{I_0}{2}{\left(cos\right)}^2({\left(90\right)}^o-{\left(30\right)}^o)$
$=\frac{I_0}{2}co{s}^{2}60^o$
$=\frac{I_0}{8}$