Fluorescent lamps produce light by using electricity to excite mercury vapor, which produces ultraviolet light. The ultraviolet light in turn causes the fluorescent lamps' phosphorescent coating to fluoresce, or glow, with visible light. Fluorescent lamps are bulkier, more complex, and more expensive than traditional, incandescent bulbs, but they are much more energy efficient and last longer, saving money in the long run. Fluorescent lamps use a ballast to control the amount of electricity that flows through the lamp, as they need only a small amount to work and would self-destruct under an uncontrolled flow.
American inventor Peter Cooper Hewitt patented the first mercury vapor lamp in 1901. The first commercial fluorescent lamps were manufactured by General Electric and appeared on the market in 1938. They were showcased a year later in the Golden Gate Exposition and the New York World’s Fair. General Electric was also awarded the patent for the invention in 1939, though it was contested by Sylvania for years to follow. Fluorescent lamps gained in popularity throughout World War II, and by 1951, more lighting was produced by fluorescent lamps than by incandescent bulbs in the United States.
Until fairly recently, fluorescent lamps were used only in institutional and large commercial buildings. The compact fluorescent lamp (CFL), suitable for home use, was invented in the 1970s and did not become commercially available until the early 1980s. However, when it first appeared on the market, the CFL was very expensive, the equivalent of 30 US dollars today. The spiral design of most CFLs available today was invented by Edward Hammer of General Electric in 1976, but it did not reach consumers until 1995.
Home use of fluorescent lamps is still low in most countries, but the idea is gaining in popularity with the increase in awareness about energy conservation. Incandescent bulbs are now very rare in East and Southeast Asia, and Australia and Canada have enacted plans to phase out incandescent lamps within a few years. Fluorescent lamps can last 10 to 20 times as long as incandescent lamps, and current models produce a glow nearly indistinguishable from that of a traditional light bulb.