Question

An unpolarised beam of intensity $I_0$ is incident on a pair of Nicol prisms making an angle of ${60}^{\circ }$ with each other. The intensity of light emerging from the pair is-

• A. $I_0$
• B. $\frac{I_0}{2}$
• C. $\frac{I_0}{4}$
• D. $\frac{I_0}{8}$

Answer 1

The correct option is D $\frac{I_0}{8}$


After passing form through first Nicol prism the intensity will be reduce by $50\%$

$I^{\prime }=\frac{I_0}{2}$

Then it will pass from the second Nicol prism and which makes an angle ${60}^{\circ }$with the first one.

According to Malus law,

$I=I_0{\cos }^2\theta =I_0{\cos }^2\left({60}^{\circ }\right)[\because I_0=I^{\prime }]$

$I=\frac{I_0}{2}\times {\left(\frac{1}{2}\right)}^2=\frac{I_0}{8}$

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> Hence, $\left(D\right)$ is the correct answer.