How does the sense of sight work?
September 27, 2012
By: Will P.
Introduction:
The eye is a very special part of the body. Sight is one of five senses the other four are taste, touch, smell and hearing. If you did not have eyes you would not be able to see anything. You would not know where to go. The eyelid protects the eye and spreads tears from tear ducts to wash the eye.The eye lashes protect the eye by preventing small particals from getting in your eye.
Different shaped eyes:
Digram of the eye 2.gif
Figure 1. Parts of the eye


People that can see far away have shorter eyes and people that have egg shaped eyes can see close up.

The pupil:
The pupil is a black hole in the middle. If there is too much light the pupil will get smaller and if there is not enough light the pupil will get bigger, allowing more light to come in. The iris is the colored part of your eye. Light colored eyes are more sensitive than dark colored eyes because dark colored eyes have more protective pigment in the iris than light colored eyes.
How you see:
Parts of the eye.jpg
Figure 2. Parts of the eye


The cornea is a tough clear dome of transparent cells which protects the iris and pupil from damaging light rays. Behind the cornea is fluid which holds the lens in place. Beams of light first pass through the cornea, then fluid, and then the iris and lens. When the light rays get to the lens the lens bends the light rays to form a clear image. The lens focuses the light so we can see. The light rays cross before they hit the retina making the image upside down on the back of the eye. The brain flips the image upside down again so the image appears right side up.

Photoreceptors:
Photoreceptors are light receiving cells that make up the retina. There are two kinds of photoreceptors. They are called rods and cones. They detect light rays turning the light rays into an image. Cones detect color and sharp detail while rods detect shades of black, white, and gray.
The eye powerpoint.jpg
Figure 3. How the eye works

Your blind spot:
Your blind spot is the place where the optic nerve is connected to the retina. It is called the blind spot because you can not see in that spot. The optic nerve sends signals to the brain telling it information about the image.
Glossary:
Cornea: a tough clear dome that covers and protects the iris and [[#|lens of the eye]]
Iris: the colored portion of the eye that surrounds the pupil
Photoreceptors: light receiving cells
Pupil: a black hole in the center of your eye that allows light to pass through
Retina: the back of the eye ball where the lens focuses the image
Citations:

“How the Eye Works.” The [[#|Vision correction]] website. Internet media services, Inc., 1996. Web. Sep. 25 2012.

Platt, Richard. Incredible Body. New York: New York DK, 1998. Print.

“The Eye.” Compton’s by Britannica. Encyclopedia Britannica [[#|Online School]] Edition.Encyclopedia Britannica, Inc., 2012. Web. 27 Sept. 2012.

Weiss, Ellen. The Sense of Sight. New York: Children’s Press, 2009. Print