Final answer:
The iris, which is the colored part of the eye, is responsible for controlling the amount of light that enters the eye by adjusting the size of the pupil.
Step-by-step explanation:
The component responsible for controlling how much light enters the eye is the iris. The iris is the colored part of the eye surrounding the pupil, and it includes muscles that adjust the pupil's size. The pupil is the opening through which light enters the eye, and the iris modulates this opening in response to light intensity. In bright light, the iris contracts, making the pupil smaller to let in less light. In dim light, the iris relaxes, allowing the pupil to dilate and admit more light. This adjustment process is known as the pupillary light response. The cornea is the eye's outermost layer and helps to focus incoming light, but it is not responsible for regulating the amount of light that enters.