What are fluorescent tubelight made up with?

Fluorescent tube lights are made up of a glass tube filled with a low-pressure gas, typically argon or neon, along with a small amount of Mercury vapor. The inner surface of the tube is coated with a phosphorescent material that emits visible light when excited by ultraviolet (UV) radiation produced by the mercury vapor. When electricity passes through the gas, it ionizes, creating UV light that then activates the phosphor coating, resulting in the illumination characteristic of fluorescent lights.