Light and the Human Eye – We learned that the cornea is the first part of your eye that light rays travel through. It is a convex lens made of transparent tissue. The iris controls the amount of light entering the eye. The pupil is an opening that leads to the inside of your eye. In bright light the iris relaxes and the pupil becomes smaller. In dim light the iris contracts and the pupil becomes larger. Then we learned that behind the iris is the lens which is transparent tissue that helps focus an object. The back of the eye has a layer of light-sensitive cells called the retina on which images form. Rod cells in the retina fire when the levels of light are low. Cone cells in the retina fire when light levels are high. Three types of these cells are sensitive to different wavelengths of light allowing us to see colors.
The Colors of Objects – We learned that the colors of an object depend on the wavelength of the light waves it reflects. When light waves of different wavelengths interact with an object, the object absorbs some light waves and reflects others. The wavelengths of light waves absorbed and reflected depend on the materials from which the object is made. When reflected light comes in contact with your eye, the cone cells in your retina send nerve signals to your brain. The color that an object appears to be depends in part on the color of the light shining on it. Then we learned that white light is a combination of light of many different colors.