The document discusses different types of light sources: - Incandescent light bulbs produce light by heating a filament to high temperatures. Most of the energy is released as heat. - Fluorescent lights use electricity to excite mercury vapor which produces ultraviolet light, causing a phosphor coating to glow and produce visible light. They are more energy efficient but harder to dispose of than incandescent lights. - Phosphorescent materials continue to glow for a period of time after the light source is removed by slowly releasing stored energy. - Chemiluminescent and bioluminescent reactions produce light through chemical processes in glow sticks and deep sea creatures. - Light is a type of electromagnetic wave.