|If you close your eyes nothing can be seen. This is because no light reaches your eyes. You see things because light bounces off them, and then this light enters your eyes. In other words, objects reflect light, and we see the reflected light.
Rays of the light first pass through the cornea, a transparent covering on the outside of the eye. Next the light goes through the pupil, which is a hole in the middle of the iris. The iris, the colored part of the eye, helps the pupil open and close. On a bright sunny day, the iris makes the pupil grow smaller to let in less light. In a dark room, such as a theatre, the iris makes the pupil grow wider to let in more light.
After light rays pass through the iris, they go through the lens. Muscles attached through the lens change its shape just a little bit, to help the lens focus. The lens focuses the light rays onto the surface at the back of the eyeball, called the retina.
Inside the retina, light rays change into electrical signals. These signals travel along the optic nerve to the brain. The brain makes sense of the signal and recognizes the image as, for example, a tree, a cat, car, etc. It all happens so fast that it cannot be noticed. All you do is open your eyes and see.
In some peopleís eyes, the lenses donít change and focus well as they should. Those are the people who need glasses. A person who can see things close up but needs glasses to focus on things far away is called nearsighted. A person, who can see things far away but needs glasses to focus on things close by in order to read, is called farsighted. Glasses made of differently shaped lenses correct each of those seeing problems. There are even glasses designed to help people see both far away and close up. They are called bifocals.
Directions: Answer the following questions.