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The quest to bring light to the world

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Two carbon filament bulbs, notice how the glass appears grey thanks to carbon sublimation coating the interior. (Image: Ulf Seifert via Creative Commons)

It was only a couple of centuries ago that great improvements were made in the quest to bring light to the world. For hundreds of years, lamps used oil, beeswax, kerosene, coal gas or natural gas, all of which came with the danger of burning down whatever they were near. A better light source was needed, and the quest for a better light source continues to this day.The first arc lamp was invented in 1809 when Humphrey Davy, a British chemist, used a battery and two charcoal strips to produce incandescent light. Arc lamps were used to light the streets of Paris in 1841 on an experimental basis, but they proved to be too short-lived to be practical.

In 1879, Thomas Edison and Joseph Swan, a British chemist, separately developed an incandescent lamp using a carbon fiber filament (though Swan obtained the first patent). In 1881 the Savoy Theater in London was the first public building to be lit by electricity.

Around the turn of the century, other elements like osmium and tantalum were used for the filament because of their higher melting points. The goal was to maintain the brightness of the bulb while still preserving the long life of the bulb. Operating bulbs at lower temperatures extended their life span, but of course produced less light as a result.

A breakthrough came in 1906, when the General Electric Company and William Coolidge developed bulbs made of tungsten filaments. Tungsten proved to be far superior than anything in use previously. It had a higher melting point than other materials and a high tensile strength; however, when the tungsten would sublime (convert from a solid to a gas), it would coat the inside of the bulb with a black film, reducing the light output.

To counter this, gases such as nitrogen and argon were added to the bulb to reduce sublimation. These gases in turn reduced the heat output of the filament, lowering the heat and light output. To counter this effect, the filament was wound into a coil, which reduced the loss of heat. This is the design that is in use today.

Because incandescent light bulbs are very inefficient (over 90% of the energy is expended in the form of heat rather than light), fluorescent light bulbs came to be more popular during the Energy Crisis of the 1970s.

Fluorescent bulbs have been around in one form or other almost as long as incandescent bulbs. In 1896 Thomas Edison patented a lamp that used x-rays. However, Edison abandoned research with x-rays after nearly losing his sight and after his laboratory assistant, Clarence Dally, lost his left arm and right hand due to radiation exposure. After this experience Edison famously said, "Don't talk to me about X-rays. I am afraid of them."

In 1901 Peter Cooper Hewitt developed the first commercially viable mercury vapor lamp.  Other attempts at fluorescent lamps created bulbs that glowed green instead of white. Some used phosphor; others used neon and argon gas.

However, it wasn't until 1934 that Richard Thayer, George Inman and others developed the first modern fluorescent lamp with white light. And in 1976, Ed Hammer invented the compact fluorescent light (CFL) which has become the standard in lighting efficiency. That may be coming to an end, however.

Beginning in 2013, a new bulb will be produced which may eliminate the familiar fluorescent bulb altogether. David Carroll, professor of physics at Wake Forest University in North Carolina, has invented a new type of light using field-induced polymer electroluminescent technology — the Fipel bulb. Electric current is passed through nanomaterials, causing them to glow inside a white-emitting polymer. The light can be made into any shape and any spectrum, so the harsh flickering blue-white light emitted by fluorescent tubes will one day be replaced with an energy-efficient version that can mimic sunlight or provide any type of tint.

The Fipel bulb is more energy-efficient than fluorescent bulbs and doesn't contain mercury, which is an issue with fluorescent bulb disposal. The bulbs also don't break, since they are made of a polymer instead of glass.

Also coming to stores in the near future are LED bulbs that will give off the same light as a 60-watt incandescent bulb using only a tenth of the wattage. A single bulb may cost $20 or more, but may last two decades with regular use. The quest for a better, more energy-efficient way to light the world continues.

Author

Susan Borowski

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