Your eyes function similarly to a camera. Light from the surrounding environment passes through the lens and is recorded on the retinas at the back of your eyes. The information from your retinas is then sent to your brain, where it is converted into awareness of objects around you.
Light
It's a slightly startling fact that the world around you is devoid of colour. There are only surfaces that reflect sunlight at different wavelengths. Your eye interprets the light reflected by these surfaces, and as a result, you perceive objects to have the colour wavelength that they reflect. Light enters your pupil and is focused by the cornea onto the lens by everything around you. The lens focuses the light even more and flips it onto the back of the retina. The optic nerve transmits this information to your brain. A large portion of your brain is dedicated to vision perception, yet little is known about the brain's role in vision.
Pupil and Cornea
When light enters the pupil, it either expands or contracts. This movement modifies the amount of light that enters the eye. By looking closely at a person's eye when she is looking at a bright object, you can see the pupils expanding and contracting. As more light enters the pupil, it contracts, allowing less light to pass through. When there is less light entering the eye, the pupil dilates to allow more light in. The transparent cornea focuses light that has passed through the pupil onto the lens.
The Lens
The lens of a human eye, unlike the cornea, is adjustable. It has the ability to move, allowing the eye to focus on distant objects and produce a sharper image on the retina. The lens and cornea work together to provide humans with a sharp focus on both near and far objects. Light reaches the retina after being focused by the lens.
The Retina
The retina is the eye's inner surface. The retina receives an image of the world around you from light focused through the pupil, cornea, and lens. It functions similarly to camera film in that it chemically reacts to light and transmits information to the optic nerve. As a result of the red-eye effect, the retina is sometimes visible in photographs.