The focal length of a lens of camera is 5f and that of another is 2.5f what is the time of exposure for the second if for the first one is 1/200 sec? a)1/200 b)1/800 c)1/6400 d)1/3200
ayusha , 7 Years ago
Grade 11
1 Answers
Arun
Last Activity: 7 Years ago
Dear student
f = focal length/aperature
f number decrease by 2
Time of exposure should decrese by 2² = 4
Hence time of exposure = (1/4)*(1/200) = 1/800
Regards
Arun (askIITians forum expert)
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