1.45. How the Eye Works http://www.ck12.org
1.45 How the Eye Works
- Explain how the eye works to produce images.
How do you see the board?
As you are sitting in the classroom, you may at first be focused on a paper directly in front of you. Then you may
look to the front of the room to see a math problem worked out on the board. How can your eyes focus directly in
front of you and then, a second later, at a distance? Your eyes are rather amazing!
How the Eye Works
The job of the eye is to focus light. The parts of the eye (Figure1.87) help it to carry out its job. Follow the path of
light through the eye as you read about it below.
Vision involves sensing and focusing light from people and objects. The steps involved are as follows:
- First, light passes through the cornea of the eye. Thecorneais a clear, protective covering on the outside of
the eye. - Next, light passes through the pupil. Thepupilis a black opening in the eye that lets light enter the eye.
- After passing into the eye through the pupil, light passes through the lens. Thelensof the eye is a clear,
curved structure. Along with the cornea, the lens helps focus light at the back of the eye. This is pictured
below (Figure1.88). - The lens must bend light from nearby objects more than it bends light from far-away objects. The lens changes
shape to bend the light by just the right amount to bring objects into focus. - The lens focuses light on theretina, which covers the back of the inside of the eye. The retina has light-sensing
cells called rods and cones.Rodslet us see in dim light.Coneslet us detect light of different colors. - When light hits rods and cones, it causes chemical changes. The chemical changes start nerve impulses. The
nerve impulses travel to the brain through theoptic nerve.