Explanation

(a) A camera is a device used to take pictures, either singly or in sequence. Camera’s have a lens positioned in front of the camera’s opening together the incoming light and to focus the image or part of the image on the recording surface. The size of aperture (its diameter) controls the brightness of the scene control and the amount of light that enters the camera during a period of time, and the shutter controls the length of time that the light hits the recording surface.
A diameter of an aperture is measured in $f$- stops. A lower $f$- stops number opens the aperture admits more light onto the camera sensor. Higher $f$ – stop numbers make the cameras aperture smaller so less light hits the sensor.