Final answer:
The cornea, aqueous humor, and lens are the three structures of the eye that refract light rays, playing a critical role in focusing light onto the retina for clear vision.
Step-by-step explanation:
The three structures of the eye that refract light rays are the cornea, the aqueous humor, and the lens. These structures have greater refractive indices than air, which allows them to bend the light rays towards the retina. The cornea contributes about two-thirds of the refractive power due to the significant change in the speed of light when it passes from air to the cornea.
The lens then fine-tunes this focusing, enabling sharp images of objects at varying distances. This process is vital for vision, as it ensures that light rays converge correctly on the retina, where photoreceptor cells like rods and cones detect the light and send nerve impulses to the brain to produce the images we see.