Physics · 2010
NEET 2010 · Prelims · Code A · Q23
A lens having focal length f and aperture of diameter d forms an image of intensity I. Aperture of diameter d/2 in central region of lens is covered…
A lens having focal length $\displaystyle f$ and aperture of diameter $\displaystyle d$ forms an image of intensity I. Aperture of diameter $\displaystyle \frac{d}{2}$ in central region of lens is covered by a black paper. Focal length of lens and intensity of image now will be respectively:
Official answer
(4)
$\displaystyle f$ and $\displaystyle \frac{3 \mathrm{I}}{4}$
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