Which part of the eye is primarily responsible for focusing light?

The lens is the primary part of the eye responsible for focusing light. It adjusts its shape to help focus light rays onto the retina, which allows us to see clearly at different distances. When viewing objects that are close, the lens becomes thicker to bend the light rays more sharply, while for distant objects, it flattens out. This process is known as accommodation.

The cornea also plays a significant role in focusing light, as it bends light when it first enters the eye, but its contribution is not as flexible or variable as that of the lens. The pupil, on the other hand, functions as an aperture that regulates the amount of light entering the eye, but it does not have a role in focusing that light. The optic nerve is responsible for transmitting visual information from the retina to the brain, but it does not participate in the focusing process itself. Thus, the lens is the key structure involved in adjusting focus and ensuring that images are clear.