Question

A beam of unpolarized light is passed first through a tourmaline crystal $A$ and then through another tourmaline crystal $B$ oriented so that its principal plane is parallel to that of $A$. The intensity of final emergent light is $I$. The value of the $I$ is

• A. $\frac{I_o}{2}$
• B. $\frac{I_o}{4}$
• C. $\frac{I_o}{8}$
• D. none of these

Answer 1

The correct option is A $\frac{I_o}{2}$

When the unpolarized light falls on the first tourmaline crystal, the intensity of the light halves and becomes polarized.

Thus $I_1=\frac{I_0}{2}$

When this polarized light falls on the next tourmaline crystal at an angle $\theta$, the intensity of light becomes,

$I_2=I_{1}co{s}^2\theta =I_{1}co{s}^2{0}^{\circ }$

$=\frac{I_0}{2}$