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  4. Two polaroids A and B are placed with their polaroid axes 30o to each other as shown in the figure. A plane polarised light passes through the polaroid A and after passing through it, intensity of light becomes I0 . What is the intensity of finally transmitted light, after passing through the polaroid B ? <img class=img-fluid question-image alt=Question src=https://cdn.tardigrade.in/q/nta/p-5x8pntwp7ueq.png />

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Q. Two polaroids $A$ and $B$ are placed with their polaroid axes $30^{o}$ to each other as shown in the figure. A plane polarised 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 $B$ ?

Question

NTA AbhyasNTA Abhyas 2020Wave Optics

Solution:

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