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The National MagLab is funded by the National Science Foundation and the State of Florida.

Fluorescent Lamps – 1934

Compared to incandescent lamps, fluorescent lamps last longer, require less energy and produce less heat, advantages resulting from the different way in which they generate light.

Fluorescent Lamps – 1934

Today fluorescent lamps light up our lives. They illuminate stores, streets and offices, and are even becoming common for certain uses in homes. Compared to incandescent lamps, fluorescent lamps last longer, require less energy and produce less heat, advantages resulting from the different way in which they generate light.

Incandescent lamps contain a thin filament, typically made of tungsten, through which electricity runs. The filament’s resistance to the electricity causes it to heat up and glow. A fluorescent lamp, on the other hand, contains no filament. Instead, it features two electrodes, one at each end of a long, cylindrical bulb. Inside the bulb is a gas (normally argon) and mercury vapor. As electrons travel from one electrode to another, they excite mercury atoms. When these atoms settle back into an unexcited state, they give off photons of ultraviolet light. The human eye cannot detect this light naturally. Instead, a phosphor that coats the inside of the bulb gives off visible light when it is hit with ultraviolet photons.

Geissler tubes and Crookes tubes were both predecessors of the fluorescent lamp. These evacuated cylinders containing electrodes were used for scientific, educational and entertainment purposes, but not as practical lighting. Not until the late 1800s and early 1900s did entrepreneurial scientists begin to develop fluorescent bulbs as light sources. Nikola Tesla and Daniel McFarlane Moore, both one-time employees of Thomas Edison, were two of the earliest men to develop and sell primitive versions of the fluorescent lamp. A few years after their work, at the dawn of the 20th century, Peter Cooper Hewitt brought the lamp much closer to its modern design when he filled the bulbs with mercury vapor. The light the Hewitt lamp emitted, however, was blue-green rather than white, making it poorly suited for most purposes despite its efficiency.

Some 20 years later, Edmund Germer succeeded in making the fluorescent lamp emit a uniform white light. The Berlin native realized that by using a special coating on the inside of the bulb, he could transform the energy from ultraviolet radiation into a white light perceptible to the human eye. Germer also developed a form of the fluorescent lamp that increased the vapor pressure inside the bulb.

In America, the General Electric company was the next big player in the history of the fluorescent lighting, buying the patent rights to Germer’s lamp. The company modified the design under the leadership of George Inman to make it more practical, dependable and ready for large-scale production. The design was completed in 1934, but GE did not begin selling lamps until a few years later because they needed to build factories and the machinery necessary for manufacturing. While GE was finalizing plans in America, fluorescent bulbs were already being released in Europe (the first in 1934) by an unrelated company, General Electric Co. Ltd. in London. Other competitors began to enter the market at about the same time as the American GE company, but none was as successful. By 1938, GE had made the fluorescent lamp a viable and often preferable alternative to the incandescent light. Today, compact fluorescent light bulbs are becoming increasingly popular in homes and businesses as an energy-saving alternative to incandescent.