A fluorescent lamp, or fluorescent tube, is a type of electric light that produces visible light when an electric current passes through it. It consists of a glass tube filled with a gas, usually argon or mercury vapor, and a phosphor coating on the inside of the tube. When the electric current passes through the gas, it produces ultraviolet (UV) light, which then causes the phosphor coating to fluoresce, producing visible light. Fluorescent lamps are more energy efficient than incandescent lamps and are used in a variety of applications, including lighting for homes, offices, and industrial buildings.