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QJEEM21Ph1c1e: JEE Main 2021 Physics - Class 12 JEEM21Ph1c1e Solution: A source of light is placed in front of a screen. Intensity of…

A source of light is placed in front of a screen. Intensity of light on the screen is I. Two Polaroids P1 and P2 are so placed in between the source of light and screen that the intensity of light on screen is I/2. P2 should be rotated by an angle of (degrees) so that the intensity of light on the screen becomes 3I8{{3I} \over 8} .

Step-by-Step Verified Solution

I=I02cos⁡2ϕI = {{{I_0}} \over 2}{\cos ^2}\phi

JEE Main 2021 (Online) 26th August Evening Shift Physics - Wave Optics Question 72 English Explanation

I02cos⁡2ϕ=3I8{{{I_0}} \over 2}{\cos ^2}\phi = {{3I} \over 8}

cos⁡2ϕ=34{\cos ^2}\phi = {3 \over 4}

cos⁡2ϕ=32{\cos ^2}\phi = {{\sqrt 3 } \over 2}

⇒ϕ=30\Rightarrow \phi = 30

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