# If intensity after passing through a polaroid is 100 Lumen. Now this same polaroid is rotated by 30° about it's axis

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If intensity after passing through a polaroid is 100 Lumen. Now this same polaroid is rotated by 30° about it's axis then find new intensity after passing through it.

(1) 50 Lumen

(2) 100 Lumen

(3) 25 Lumen

(4) 65 Lumen
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Wave optics, polarization

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Ans. (2) 100 Lumen

Sol. $I_{P_1}=I_{P_2}=100$ Lumen

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just have a look on  official answer key generated by nta ....the answer of this question is 75. Also, it's an integer type question
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I think when this question came in exam it is of integer type and answer must be 75.

logic: after passing through the polarizer for the first time intensity becomes half that is equal to 100.

after that from malus' law I/2cos^2(theta) , where theta=30 degree so it is equal to 75 on solving.