Question

Amount of light entering into the camera depends upon :

• A. focal length of objective lens
• B. product of focal length and diameter of the objective lens
• C. distance of objective from camera
• D. aperture setting of the camera

Answer 1

The correct option is D aperture setting of the camera

An aperture is an hole through which light light enters the camera, if $N$ is the f-number, $f$ is focal length and $D$ the diameter of hole then amount of light entering into the camera is proportional aperture area.

$Area=\frac{\pi D^2}{4}=\pi {\left(\frac{f}{2N}\right)}^2$

Thus option D is correct.