Where are the photoreceptors located within the eye?

Photoreceptors, which are specialized cells responsible for converting light into electrical signals that can be processed by the brain, are located in the retina. The retina is a thin layer of tissue situated at the back of the eye. It contains two main types of photoreceptors: rods, which are sensitive to low light levels and are responsible for night vision, and cones, which are responsible for color vision and function best in bright light.

The other structures mentioned, such as the cornea, lens, and iris, serve different functions. The cornea is the eye's outermost layer, providing protection and helping to focus light. The lens further focuses light onto the retina, and the iris controls the amount of light that enters the eye by adjusting the size of the pupil. However, none of these structures contain photoreceptors. Thus, the retina is the correct answer since it is the only part of the eye that contains the photoreceptors necessary for vision.