What term refers to the control of the amount of light entering the eye?

The iris is the correct answer because it is the part of the eye that regulates the size of the pupil, which in turn controls the amount of light that enters the eye. The iris is a circular muscle that can expand or contract to open or close the pupil, responding to changes in lighting conditions. In bright light, the iris constricts the pupil to limit the amount of light entering, protecting the retina from excessive brightness. In low light, the iris dilates the pupil to allow more light in, enhancing vision.

The pupil itself is simply the opening at the center of the iris, and while it does change size, it does so as a result of the iris's actions. The cornea, being the clear front part of the eye, provides an initial refraction of light but does not control light intake. The lens, located behind the iris and pupil, focuses light onto the retina but does not adjust the amount of light entering the eye. Hence, the role of controlling light intake is specifically attributed to the iris.