A photographic plate is placed directly in front of a small diffused source in the shape of a circular disc

Monjur Alahi

A photographic plate is placed directly in front of a small diffused source in the shape of a circular disc. It takes 12 s to get a good exposure. If the source is rotated by 60° about one of its diameters, the time needed to get the same exposure will be

(a) 6 s

(a) 6 s

(c) 24 s

(d) 48 s.


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Salim Ahmed Kawsar

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The correct answer is
(c) 24 s

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