An incandescent light source is a type of light source that produces light by heating a material until it glows. The material that is heated is usually a metal, such as tungsten. Fluorescent lamps, LED lamps, and neon lamps are all examples of non-incandescent light sources. Fluorescent lamps produce light by passing an electric current through a gas, which causes the gas to emit ultraviolet light. The ultraviolet light then causes a coating on the inside of the lamp to fluoresce, which produces visible light. LED lamps produce light by passing an electric current through a semiconductor material, which causes the material to emit photons. The photons then produce visible light. Neon lamps produce light by passing an electric current through a gas, which causes the gas to emit visible light.