Question

Two polaroids are kept crossed to each other. Now one of the polaroids is rotated through an angle ${45}^0$. The percentage of incident light now transmitted through the system is:

• A. 15%
• B. 25%
• C. 50%
• D. 60%

Answer 1

Answer: (B)

25%

$Given:$ Angle$={45}^o$

$Solution:$ Let the intensity of unpolarized light be $I_0$, so

the intensity of the first polaroid is $\frac{I_0}{2}$

On rotating through ${45}^{\circ }$, the intensity of light

from second polaroid $I=\left(\frac{I_0}{2}\right)(cos45{)}^2=\frac{I_0}{2}\frac{1}{2}=\frac{I_0}{4}=0.25I_0$

$\therefore$ percentage of incident light transmitted

through the system $=25\%$

$So,the$ $correct$ $option:B$