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. Then we answered questions identifying electromagnetic waves.