A point source S emits unpolarized light uniformly in all directions. At two points A and B , the ratio r=I_A / I_B of the intensities of light is 2. If a set of two polaroids having 45^ angle between their pass-axes is

Correct answer: 0 (I (1)/(l^2)) Where I: distance from point source. aligned & (I_A)/(I_B)=(I_B^2)/(I_A^2)=2 & I_B= 2 I_A . aligned ) Also, due to polaroids: aligned & I_B^ =(I_B)/(2) ^2 45^ =(I_B)/(4) & I_B^ =(I_B)/(4) (2) & Ratio becomes 4 times. & r_ new =8 aligned )

JEE Advanced 2024Paper 1

Exam: JEE Advanced
Year: 2024
Paper: Paper 1
Subject: Physics
Chapter: Wave Optics

JEE Advanced 2024 · Paper 1 · Physics · Wave Optics

A point source S emits unpolarized light uniformly in all...

A point source

\mathrm{S}

emits unpolarized light uniformly in all directions. At two points

\mathrm{A}

and

\mathrm{B}

, the ratio

r=I_A / I_B

of the intensities of light is 2. If a set of two polaroids having

45^{\circ}

angle between their pass-axes is placed just before point

\mathrm{B}

, then the new value of

r

will be ______

Correct answer

Step-by-step solution

(I \propto \frac{1}{l^2}) Where I: distance from point source.

\begin{aligned} & \Rightarrow \frac{I_A}{I_B}=\frac{I_B^2}{I_A^2}=2 \\ & \Rightarrow I_B=\sqrt{2} I_A . \end{aligned}

) Also, due

to polaroids:

\begin{aligned} & I_B^{\prime}=\frac{I_B}{2} \cos ^2 45^{\circ}=\frac{I_B}{4} \\ & \Rightarrow I_B^{\prime}=\frac{I_B}{4} \ldots \text{ (2) } \\ & \Rightarrow \text{ Ratio becomes } 4 \text{ times. } \\ & \Rightarrow r_{\text{new }}=8 \end{aligned}

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