KS3 Science Revision

We see things because light reflects into our eyes. Lenses in our eyes can be used to focus light. A lens refracts light. A convex ray bulges outwards and causes the light rays to converse. We have a convex lense in each of our eyes. It is called the cornea and it does most of the eye's focusing. Behind that is the convex lens which changes shape to focus light on objects at varying distances. The iris is the coloured part of the eye. It controls how much light is entering the eye. Finally, the image is formed on the retina. Light energy is transfered from a light source to an absorber. When lights waves hit the retina, it causes chemical and electrical changes which sends a message to the brain.