With diaphragm of the camera lens set at `(f)/(2)` , the correct exposure time is `(1)/(100)` , then with diaphragm set at `(f)/(4)`. Calculate the correct exposure time.

Explanation

`t_(1) prop . (f^(2))/([(f)/(2)]^(2)) " and " t_(2) prop .(f^(2))/([(f)/(4)]^(-2))`
`t_(1)= (1)/(100) , t_(2) = ? (t_(2))/(t_(1)) = (16)/(4) = 4`
or `t_(2) = 4t_(1) = (4)/(100) s`