First slide

Polarisation

Question

Two polaroids $P_{1} and P_{2}$ are placed with their axis perpendicular to each other. Unpolarised light $I_{0}$ , is incident on $P_{1}$ . A third polaroid $P_{3}$ is kept in between $P_{1}$ and $P_{2}$ such that its axis makes an angle 45° with that of $P_{1}$ . The intensity of transmitted light through $P_{2}$ is

Moderate

A

$\frac{I_{0}}{4}$
B

$\frac{I_{0}}{8}$
C

$\frac{I_{0}}{16}$
D

$\frac{I_{0}}{2}$

Solution

The intensity of transmitted light through $P_{1}$
$I_{1} = \frac{I_{o}}{2}$
The intensity of transmitted light through $P_{3}$
$I_{2} = I_{1} \cos^{2} 45 °$
$= \frac{I_{o}}{2} {(\frac{1}{\sqrt{2}})}^{2} = \frac{I_{o}}{2} \cdot \frac{1}{2} = \frac{I_{o}}{4}$
$Angle between polaroids P_{3} and P_{2} = (90 ° - 45 °) = 45 °$
$∴ Intensity of transmitted light through P_{2},$
$I_{3} = I_{2} \cos^{2} 45 ° = \frac{I_{o}}{4} {(\frac{1}{\sqrt{2}})}^{2} = \frac{I_{o}}{8}$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App