Fluorescent and incandescent lights use different mechanisms to produce visible light; incandescent lights rely on light emitted by a heated filament, while fluorescent lights utilize ultraviolet light emitted by excited mercury particles. The process behind fluorescent lighting is more complex than that of incandescent lights. However, fluorescent lamps are a more energy-efficient method of lighting than incandescent lamps.
Incandescence is the emission of light by a hot object. Incandescent light bulbs function by stimulating the incandescence of the filament, a wire inside the bulb. Electricity passes through the filament and raises it to high temperatures until it is so hot that it produces light. The glass bulb surrounding the filament keeps oxygen out of the system in order to prevent the filament from burning or evaporating.
Fluorescent lamps use another method entirely. The fluorescent tube is filled with mercury vapor gas. When the lamp is turned on, electrical currents excite the mercury vapor, causing it to emit ultraviolet light. However, because ultraviolet light is not visible to the human eye, the inside of the fluorescent tube is coated with phosphor. This phosphor coating converts ultraviolet rays to visible light.
Fluorescent lights have higher luminous efficacy than incandescent lights. This means that they convert more of the input power to visible light (incandescent lights convert most of the electrical energy to heat). Whereas incandescent lights convert approximately 5 percent of power input to visible light, fluorescent lights convert about 22 percent.