1) Refraction occurs when light passes from one medium to another, causing its speed and direction to change. As light passes from air into water, its speed decreases and its path bends toward the normal line. 2) Lenses use refraction to bend light rays. A converging lens brings light rays to a focal point on both sides of the lens, forming real, inverted images. A diverging lens spreads light rays out, forming virtual, upright images. 3) Ray diagrams use three rules to model how light rays bend when passing through lenses and mirrors, predicting image location, size, and orientation. Converging lenses are used in eyes, cameras, and magnifying glasses to focus light