A compact fluorescent lamp (CFL) is a type of fluorescent lamp designed to replace an incandescent light bulb. The folded tube of a CFL light bulb contains argon and mercury vapor, and the inside of the tube is coated with a fluorescent paint. When an electric current is driven through the tube, it generates invisible ultraviolet light that excites the fluorescent coating on the inside of the tube, producing visible light. CFLs are highly energy-efficient, using up to 75% less energy than incandescent bulbs. They also have a longer lifespan, with some models rated up to 15,000 hours. However, CFLs contain small amounts of mercury, which can be harmful if the bulb breaks and the mercury is released into the environment. Therefore, it is important to dispose of CFLs properly at the end of their life cycle.