The amount of light entering the eye is regulated by changes in the size of the

The eye is a complex part of your body as shown in the picture. The part of the eye that takes in the light is the pupil. This is the black dot of your eyeball that takes in the adequate amount of light to focus on the objects you see. You should note that the color black absorbs lights, while the white reflects light. An analogy would be the black hole in space that sucks all matter in its range, including radiation. That is why the function of regulating the intake of light is appropriate for the pupils.