Question

Two polaroids $A$ and $B$ are placed with their polaroid axes $30^{\circ}$ to each other as shown in the figure. A plane polarized light passes through the polaroid $A$ and after passing through it, intensity of light becomes $I_0$.What is the intensity of finally transmitted light after passing through the polaroid $B$ ?

• A. $0.25I_0$
• B. $0.5I_0$
• C. $0.75I_0$
• D. $0.866I_0$

Answer 1

Answer: (C)

$0.75I_0$

Answer 2

The intensity / of the transmitted light varies directly as the square of the cosine of the angle between the transmission direction of polariser and analyser
$I=I_{0} \cos ^{2} \theta$
Intensity of finally transmitted light after passing through polaroid $B$ is given by $I=I_{0} \cos ^{2} \theta$ (Intensity)
$I=I_{0} \cdot \cos ^{2} 30^{\circ}$
$I=I_{0} 0.75$
$I=0.75 I_{0}$
where, $I_{0}$ is the maximum intensity of transmitted light.