Which part of the eye is responsible for focusing light?

The cornea plays a crucial role in focusing light as it is the transparent, dome-shaped surface at the front of the eye. It bends or refracts light that enters the eye, helping to direct it toward the lens, which further fine-tunes the focus. The cornea provides the majority of the eye's optical power due to its curvature and refractive properties.

While the iris regulates the amount of light that enters the eye by adjusting the size of the pupil, it is not directly involved in focusing. The pupil functions as an aperture that controls light entry, but it also does not aid in focusing. The retina, located at the back of the eye, is where light is converted into neural signals for the brain to interpret, but it does not have any focusing capabilities. Therefore, the cornea is the key structure responsible for focusing light as it enters the eye.