Fluorescent lamp — gas discharge light source in which visible light is emitted mainly by the phosphor, which, in turn, glows under the ultraviolet radiation of the discharge; the discharge also emits visible light, but to a much lesser extent. Luminous efficacy of a fluorescent lamp is several times greater than incandescent lamps of similar power. The lifetime of fluorescent lamps can exceed 20 times the life of incandescent lamps while ensuring sufficient quality of power supply, ballast, and compliance with restrictions on the number of on / off.
The most common gas-discharge mercury lamps high and low pressure. High pressure lamp is used mainly in street lighting and lighting systems high power, while low pressure lamps are used for lighting in residential and industrial premises.
The first ancestor of the fluorescent lights were gas discharge lamp. For the first time, luminescence of gases under the influence of electric current was observed by Mikhail Lomonosov, passing a current through a hydrogen-filled glass globe. It is believed that the first discharge lamp was invented in 1856. Heinrich Geissler got the blue glow from the gas filled tube which was excited by using the solenoid. 23 Jun 1891, Nikola Tesla patented a system of electric lighting gas discharge lamps (patent No. 454,622), which consisted of a high voltage high frequency and argon discharge lamps previously patented (patent No. 335,787 February 9, 1886. issued by the United States Patent Office). Argon lamps are used in real time. In 1893 at the world exhibition in Chicago, Illinois, Thomas Edison showed luminescence. In 1894 M. F. Moore has created a lamp that used nitrogen and carbon dioxide, emitting a pink-white light. This lamp had moderate success. In 1901, Peter Cooper Hewitt demonstrated the mercury lamp, which emitted a light blue-green color, and thus was unsuitable for practical purposes. However, its design was very close to the modern, and had a much higher efficiency than the lamp of Geissler and Edison. In 1926 Edmund Germer and his staff proposed to increase the operating pressure within the flask and cover the flasks with fluorescent powder which converts ultraviolet light emitted by an excited plasma into more uniformly white-colored light. E. Germer currently recognized as the inventor of fluorescent lights. General Electric later bought the patent of Germer, and under the guidance of George E. Inman brought the fluorescent lights to wide commercial use by 1938. In the USSR, is considered the inventor of the lamp academician S. I. Vavilov.