Electric Lighting


This article was initially published in Today's Engineer on August 2008

Since Edison's invention of a practical incandescent bulb in 1879, electric lighting has been part of popular culture. For example, it was one of the great attractions of the world's fairs in Chicago in 1894, in Buffalo in 1901, and in St. Louis in 1904. Electric lighting made cities inviting in the evening hours; for example, it gave to Broadway the name the Great White Way. And it made homes brighter and more lively. Not surprisingly, in the early decades of the century, pop culture references to electric lighting were almost always positive. Take, for example, Charlie Chaplin's 1931 movie "City Lights," which celebrated electric lighting, both indoors and outdoors.

Despite its popularity, the incandescent lamp was quite inefficient, so engineers sought alternatives. Work in the 1920s led to two new types of lamp that were significantly more efficient — the high-pressure mercury-vapor lamp and the low-pressure sodium-vapor lamp. Both lamps were especially suitable for street lighting, and both became widely used in the 1930s. So-called discharge lamps, their electric current flows from one electrode through a gas or a metal vapor to another electrode. The mercury-vapor lamp produced a bluish light, whereas the sodium-vapor lamp emitted a monochromatic, orangish light. The latter was more efficient and enjoyed widespread adoption in Germany and the Netherlands. In other countries, including the United States, England and France, mercury-vapor lamps were preferred. The distaste for the poor color rendering of the sodium lamp was so great in the United States that some states outlawed its use for street lighting. In the recent movie, "Michael Clayton" (2007), sodium lamps are assigned partial blame for a traffic accident.

Neon lights, another type of discharge lamp, also became common in the 1930s. Movies have portrayed neon both positively and negatively. For example, in "The Postman Always Rings Twice" (1946) and "On the Town" (1949), neon lights are seen as modern and attractive, while in "It's a Wonderful Life" (1946) and "From Here to Eternity" (1953), they are associated with tawdry and decadent parts of town.

Just before World War II, still another type of discharge lighting — fluorescent lighting — appeared. Researchers had long known that discharge lamps often emitted ultraviolet light. They knew also that certain minerals converted ultraviolet light to visible light in a process called fluorescence, the re-emission of light at lower frequencies. Many attempts to develop a practical lamp — placing fluorescent materials in reflectors behind the discharge tube, in a coating inside the tube, in a coating outside the tube, or within the glass itself — came to naught. Success finally came in the late 1930s, with improved lamp design and the discovery of fluorescent materials from which one could obtain white light — light having a distribution of frequencies similar to sunlight. Fluorescent lighting was featured at the 1939 New York world's fair. Fluorescent lights appear in movies from the 1940s on, but are seldom remarked upon, though they receive negative mention in "Goodbye, Columbus" (1969) and "Clerks" (1994).

For the past 70 years, incandescent and fluorescent lights have dominated electrical lighting. The introduction of the compact fluorescent bulb in the 1970s was notable because it could be used in sockets designed for incandescent bulbs. And at the end of the century, an entirely new type of electrical lighting became economically important.

Light-emitting diodes (LEDs) were invented in 1962, and soon found use as indicator lights and for instrument and computer displays. Great advances in LED technology in the 1990s led to their widespread use in large video screens and for lighting. Many movies, such as "Hackers" (1995) and "Spider Man" (2002), feature the huge video-screens in New York City's Times Square. In the first years of the 21st century, LEDs were beginning to be used in traffic lights, automobile taillights and flashlights. In turning electricity into light, LEDs are significantly more efficient than incandescent bulbs. As the manufacturing cost of LEDs decreases, they will increasingly replace incandescent lights.