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maser

(Encyclopedia)maser māˈzər [key], device for creation, amplification, and transmission of an intense, highly focused beam of high-frequency radio waves. The name maser is an acronym for microwave amplification b...

semiconductor

(Encyclopedia)CE5 N-type and P-type crystals: In a pure silicon crystal each silicon atom (Si) is surrounded by four valence electrons. In the N-doped semiconductor, illustrated in the left-hand figure, some sil...

metric system

(Encyclopedia)CE5 metric system, system of weights and measures planned in France and adopted there in 1799; it has since been adopted by most of the technologically developed countries of the world. It is based...

rock music

(Encyclopedia)rock music, type of music originating in the United States in the mid-1950s and increasingly popular throughout much of the world. A turning point in rock music occurred in the mid-1970s in the ...

radio

(Encyclopedia)CE5 A. AM transmitter B. AM receiver radio, transmission or reception of electromagnetic radiation in the radio frequency range. The term is commonly applied also to the equipment used, especially...

fan

(Encyclopedia)fan, device for agitating air or gases or moving them from one location to another. Mechanical fans with revolving blades are used for ventilation, in manufacturing, in winnowing grain, to remove dust...

hygrometer

(Encyclopedia)hygrometer hīgrŏmˈətər [key], instrument used to measure the moisture content of a gas, as in determining the relative humidity of air. The temperature at which dew or frost forms is a measure of...

gluon

(Encyclopedia)gluon, an elementary particle that mediates, or carries, the strong, or nuclear, force. In quantum chromodynamics (QCD), the quantum field theory of strong interactions, the interaction of quarks (to ...

Gell-Mann, Murray

(Encyclopedia)Gell-Mann, Murray gĕlˈ-män [key], 1929–2019, American theoretical physicist, b. New York City, grad. Yale 1948, Ph.D. Massachusetts Institute of Technology, 1951. He was associated with the Univ....

neutron

(Encyclopedia)neutron, uncharged elementary particle of slightly greater mass than the proton. It was discovered by James Chadwick in 1932. The stable isotopes of all elements except hydrogen and helium contain a n...