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. `0.4 sec`
B. `0.02 sec`
C. `0.002 sec`
D. `0.04 sec`

Answer

B

Explanation

Time of exposure `prop (f.n umber)^(2)`
`implies(t_(2))/(f_(1))=((5.6)/(2.8))^(2)=4`
`t_(2)=4t_(1)=4xx(1)/(200)=(1)/(50)sec=0.02 sec.`