The exposure time of a camera lens at the `(f)/(2.8)` setting is `(1)/(200) ` second. The correct time of exposure at `(f)/(5.6)` is

Options

A. 0.04 s
B. 0.20 s
C. 0.40 s
D. 0.02 s

Answer

D

Explanation

` t prop ` ( f - number ) ` ""^2 prop ( 1) /(("Aperture")^ 2 ) `
`(t_ 2 ) /( 1//200) = ((f//2.8)/(f//5.6))^ 2 `
`t _ 2 = 4xx ( 1 ) /(200) = ( 1 ) /(50) = 0.02 ` sec.