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Two polaroids are placed in the path of unpolarised light beam of intensity I_(0) such that no light is emitted from the second polarisation. If a third polaroid whose polarisation axis makes an angle theta with that of the first polaroid is placed between the polaroids, then intensity of light emerging from the last polaroid is |
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Answer» `((I_(0))/(8))sin^(2) 2theta` `therefore` After first polarister, intensity `I_(0)=I_(0)//2` After second polariser, intensity `I_(2)=(I_(0))/(2) cos^(2) theta` (MALUS law) After third polariser, intensity `I_(3)=(I_(0))/(2) cos^(2) theta cos^(2) (90^(@)-theta)` (because this is at `90^(@)` angle from first polariser) `rArr I_(3) =(I_(0))/(2) cos^(2) theta sin^(2) theta=(I_(0))/(8)(2 sin theta cos theta)^(2)=(I_(0))/(8) sin^(2) 2 theta` |
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