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A photographic plate records sufficiently intense lines when it is exposed for 12 s to a source of 10 W. How long should it be exposed to a 12 W source radiating the light of same colour to get equally intense lines?

A photographic plate records sufficiently intense lines when it is exposed for 12 s to a source of 10 W. How long should it be exposed to a 12 W source radiating the light of same colour to get equally intense lines?

Grade:upto college level

1 Answers

Deepak Patra
askIITians Faculty 471 Points
8 years ago
Sol. To get equally intense lines on the photographic plate, the radiant flux (energy) should be same. S0, 10W × 12sec = 12W × t ⇒ t = 10W * 12 sec/12W = 10 sec.

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