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A lens haivng focal length and aperture ...

A lens haivng focal length and aperture of diameter d forms an image of intensity `I`. Aperture of diameter `d/2` in central region of lens is covered by a black paper. Focal length of lens and intensity of image now will be respectively.

A

`(f)/(2)` and `(1)/(2)`

B

f and `(I)/(4 )`

C

`(3f)/(4) ` and `(I)/(2)`

D

f and `(3 I)/( 4)`

Text Solution

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The correct Answer is:
D
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