Lamps in which an electric current passes through a tungsten resistance filament, enclosed in a vacume tube. The filament heats up until it glows and emits visible light.
Fluorescent lamps consists of a long, sealed glass tube with an electrode at each end; a small amount of murcury is contained within the tube. the inside surface of the tube is coated with a mixture of fluorescent powders. When an electric current is maintained through the lamp, the murcury becomes vaporized and gives off invisible ultraviolet radiationthat is absorbed by the fluoresent coating. The coating then emits visible light.