Question

Two polaroids $A$ and $B$ are kept with their transmissions axes at an angle 0 with respect to one another. If the transmitted intensity of light $I_t = 0.75 \, I_0$ where $I_0$ is the intensity of light incident on the system. The $\theta $ is

• A. $30^{\circ} $
• B. $45^{\circ} $
• C. $60^{\circ} $
• D. $90^{\circ} $

Answer 1

Answer: (A)

Here, $I_t = 0.75 \: I_0 \, \, \, \, \, \, \, \, $ ......(i)
Intensity of transmitted light is given by $I_t = I_0 \: \cos^2 \theta \, \, \, \, \, \, $ ... (ii)
Comparing eqn. (i) with (ii),
$ cos^2 \theta = 0.75 = \frac{3}{4}$
$ \cos \theta = \frac{\sqrt{3}}{2} = \cos 30^{\circ} $ or $\theta = 30^{\circ} $