Which part of the eye is responsible for controlling the amount of light entering?

The pupil is the part of the eye responsible for regulating the amount of light that enters. It is an opening located in the center of the iris, which is the colored part of the eye. The size of the pupil can change in response to various light conditions; it constricts in bright light to reduce the amount of light entering the eye and dilates in low light to allow more light to enter. This adjustment helps protect the sensitive structures at the back of the eye and enhances visual clarity.

The lens, while important for focusing light onto the retina, does not directly control light entry. The cornea contributes to the eye's overall optical power and provides a protective layer but does not adjust the amount of light that passes into the eye. The retina is where light is converted into neural signals but is not involved in regulating light intensity entering the eye. Hence, it is the pupil that plays this critical role in light regulation.