Seeing

Sight is the most important of all our senses. Our eyes tell us most about the world around us.

Like most other animals, i have two eyes. I can find the reason for this. Close one eye and ask a friend to hold the pencil in front of me. Probably i will miss it. With only one eye i can't tell how far away the pencil is. Now do the same thing with both eyes open, and i will probably touch the pencil first time. Using two eyes i can judge distances. This is because each of my eyes has a slightly different view.

Look at of my eyes in a mirror. Can i see it is curved? This is because is forms part of a ball, called the eyeball. Most of the eyeball is white on the outside. The only coloured part is a circle in front which i called the iris. In the middle of a iris is a black spot, the pupil, which is actually a hole that lets light into the eye.

The iris can change the size of a pupil. In very bright light, the iris closes a pupil but in dim light, the iris opens it. I can test this for myself. Sit under a light and hold a mirror in front of my face. Look at my eyes, then close them in a few minutes. Open them and look at my pupils. What do i see?

Light goes through a pupil and then through a lens. The lens bends the light rays so that they form a picture on the back of the eyeball, the retina, which sends messages about the picture on it to the brain. The brain tells us what the picture is and i see.