Question

Two polaroid sheets are placed one over the other with their axes inclined to each other at an angle $\theta$. If only $12.5$% of intensity of unpolarised light incident on the first sheet emerges out from the second sheet, the value of $\theta$ is

• A. ${45}^{\circ }$
• B. ${90}^{\circ }$
• C. ${30}^{\circ }$
• D. ${60}^{\circ }$

Answer 1

The correct option is D ${60}^{\circ }$



Given,
Intensity of polarised light emerging out of second sheet is $I=0.125I_0$ ($\because 12.5$%)
Using
$I=\frac{I_0}{2}co{s}^2\theta$
$0.125I_0=\frac{I_0}{2}co{s}^2\theta$
$co{s}^2\theta =0.25$
$cos\theta =0.5$
$\Rightarrow \theta ={60}^o$