InterviewSolution
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InterviewSolution
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A thin lens focal length `f_(1)` and its aperture has diameter `d`. It forms an image of intensity `I`. Now the central part of the aperture up to diameter`(d)/(2)` is blocked by an opaque paper. The focal length and image intensity will change toA. `f//2,I//2`B. `f,I//4`C. `3f//4,I//2`D. `f,3I//4` |
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Answer» Correct Answer - D `Iprop aperture^(2)` `I_(1) prop pid^(2)//4 rArr I_(2)prop(pid^(2)//4-pi(d//4)^(2))` `I_(2)prop(pid^(2))/(4)(1-(1)/(4)) rArr I_(2)prop (3)/(4).(pid^(2))/(4)` `(I_(2))/(I_(1))=(3)/(4) rArrI_(2)=(3)/(4)I_(1)` |
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