One of the five senses : Sight

Nicholas Calvert, Judy (Sohyun) Chun, Sandra Frankel, Renars Dimza

How does our sense of sigh work?

Light from a source bounces off an object and enters through the eye through cornea (protective surface layer). The light then passes through the pupil controlled by the iris (muscle), into the lens. When light passes through the pupil, the size of the iris changes in order to allow a certain amount of light in.

The lens then focuses on the image, as it is squeezed by contracting muscles. The retina is filled with light sensitive cells called cones and rods; The light filters through layers of pigment in the outer layers of the cones and rods.  The rods are responsible for low light vision (black and white), and the cones are responsible for colour vision; unlike the rods, the cones require a brighter light in order to function. The rods are distributed throughout the retina, mostly along the edge of the field of vision, however there are none at the fovea and the blind spot. The cones are mostly near the fovea and far fewer are present in the retina.

The cones and rods are connected through cells in the retina to the nerve fibres in the optic nerve. When the cones and rods are stimulated by light, the nerves send off electric charges through the fibres in to the brain. The image is then projected in reverse upon the retina, and the brain interprets the image right-side up. This is done in the visual cortex. The brain does not receive a photographic image rather it constructs an approximation of what is being perceived.

source:
http://en.wikipedia.org/wiki/Eye
http://www.wisegeek.com/how-does-the-sense-of-sight-work.htm