Question

A plane polarized light is incident on a polariser with its pass axis making angle $\theta$ with x-axis, as shown in the figure. At four different values of $\theta ,\theta =8^o,{38}^o,{188}^o$ and ${218}^o$, the observed intensities are same. What is the angle between the direction of polarization and x-axis

• A. ${203}^o$
• B. ${45}^o$
• C. ${98}^o$
• D. ${128}^o$

Answer 1

The correct option is A ${203}^o$

Let the angle between polarization direction and x-axis be ${\theta }^{\prime }$.

So angle between polarisation direction and pass axis of polariser is $({\theta }^{\prime }-\theta )$

Given $\theta =8^o,{88}^o,{188}^o,{218}^o$

$\therefore I=I_{o}co{s}^2({\theta }^{\prime }-\theta )$

For ${\theta }^{\prime }={203}^o$ intensities are same