SATHEE: wave-optics Question 42

wave-optics Question 42

Question: Q. 6. (i) Unpolarised light of intensity $I_{0}$ passes through two polaroids $P_{1}$ and $P_{2}$ such that pass-axis of $P_{2}$ makes an angle $θ$ with the pass-axis of $P_{1}$ . Plot a graph showing the variation of intensity of light transmitted through $P_{2}$ as the angle $θ$ varies from zero to $180^{\circ}$ .

(ii) A third polaroid $P_{3}$ is placed between $P_{1}$ and $P_{2}$ with pass-axis of $P_{3}$ making an angle $β$ with that of $P_{1}$ . If $I_{1}, I_{2}$ and $I_{3}$ represent the intensities of light transmitted by $P_{1}, P_{2}$ and $P_{3}$ determine the values of angle $θ$ and $β$ for which $I_{1} = I_{2} = I_{3}$ .

U] [OD Comptt. I, II, III 2014]

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Solution:

Ans.(i) Try yourself similar Q. 3 SATQ-II.

$\begin{aligned} (ii) & I_{1} & = Light transmitted by P_{1} I_{3} & = Light transmitted by P_{3} = I_{1} \cos^{2} β I_{2} & = Light transmitted by P_{2} & = I_{3} \cos^{2} (θ - β) \end{aligned}$

Alternatively, (Award mark to student who indicates correct value of $I_{1,} I_{2}$ and $I_{3}$ by making a diagram)

$∴ I_{2} = I_{3}$

$I_{1} \cos^{2} β \cdot \cos^{2} (θ - β) = I_{1} \cos^{2} β$

$\begin{aligned} θ = β & Also, I_{1} = I_{2} & I_{1} = I_{1} \cos^{2} θ & or \cos^{2} θ = 1 & ∴ θ = 0^{\circ} or π \end{aligned}$

Therefore $β = 0^{\circ}$ or $π$

[CBSE Marking Scheme 2014]

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wave-optics Question 42

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Wave Optics

wave-optics Question 42

Table of Contents

Engineering Preparation

Medical Preparation

NCERT Books & Solutions

Important Resources

Other Resources

Syllabus

Test Platform

Sample Mock Test

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NCERT Exercise Video Solution

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