How the Eye Functions:

The eye is a complex organ of the body, and all of the aforementioned parts of the eye work together to give a person sight.

The most common way of describing how the eye works is to describe it as a camera. The pupil is the aperture through which light enters, and the retina is the film which records and sends images to the brain via the optic nerve.

Light enters the eye through objects around it. "Light is energy emitted in waves or rays." (D'Alonzo pg. 35) If an eye is to get a sharp image, the light rays must be bent when they enter the eye, which the cornea and the lens help to do, and thus provide proper focus for the retina. "Light rays can either be divergent, convergent or parallel. A light source always emits diverging rays. A convergent or parallel wave results when diverging rays reach a limiting aperture or opening, such as the pupil." (D'Alonzo pg. 35) Light is converged by a convex lens, and is diverged by a concave lens.

Each color of light has a different wavelength and energy. Red light has the longest wavelength and the least energy while violet has the shortest wavelength and the highest energy.

When a person sees something, light bounced off the object, and refracted from the cornea and the lens and an image is focused on the retina. The image is actually seen on the retina upside down, and is reversed when it is sent to the brain. Recall that the left side of the brain controls the right side of the body, and in remembering this, the fact that the left half of the visual field in each eye is sent to the right half of the brain.

Although an eye is likened to a camera, "[t]he one major difference is that the focus of the eye is altered by changing the focal length (or power, P=1/f) of the lens, rather than by changing the distance between the lens and the retina." (www.dur.ac.uk/r.g.bower/OpticsI/optlec/node34.html)