Final answer:
Light first hits the cornea and then the lens, with the cornea providing the majority of refractive power for focusing light on the retina. The lens fine-tunes this focus. Both work together much like a single convex lens, forming an inverted image that the brain corrects.
Step-by-step explanation:
Most of the eye's refractive power is provided by two structures; of these, light first hits the cornea, followed by the lens. The cornea provides about two-thirds of the eye's focusing power due to the significant change in light speed as it enters from air into the cornea. Meanwhile, the lens provides the remaining focusing power needed to fine-tune the image formation on the retina. Together, the cornea and lens can be conceptualized as a single thin lens which directs the light rays to produce a real, inverted image on the retina. This image is, however, perceived as upright due to the brain's capacity to invert it back.