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A thin lens focal length f(1) and its ap...

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 to

A

`f/2 and I/2`

B

`f and I/4`

C

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

D

`f and (3I)/4`

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The correct Answer is:
D
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