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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

`fandl/4`

B

`(3f)/4andl/2`

C

`fand(3l)/4`

D

`f/2and(l)/2`

Text Solution

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The correct Answer is:
C
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