Columbia Encyclopedia

Search results

267 results found

electromagnetic radiation

(Encyclopedia)CE5 Electromagnetic spectrum electromagnetic radiation, energy radiated in the form of a wave as a result of the motion of electric charges. A moving charge gives rise to a magnetic field, and if ...

sideband

(Encyclopedia)sideband, any frequency component of a modulated carrier wave other than the frequency of the carrier wave itself, i.e., any frequency added to the carrier as a result of modulation; sidebands carry t...

automatic tuning control

(Encyclopedia)automatic tuning control (ATC), method or device to keep a radio or television receiver automatically tuned to a desired frequency or channel. Assuming that the receiver is at least approximately tune...

cycle

(Encyclopedia)cycle, in astronomy, period of time required for the recurrence of some celestial event. The length of a cycle may be measured relative to the sun or to the fixed stars (see sidereal time). A frequent...

Conon

(Encyclopedia)Conon kōˈnŏn, –nən [key], 3d cent. b.c., Greek astronomer and mathematician of Samos. He traveled in the western part of the Greek world making astronomical observations, then settled at Alexand...

Todd, Mabel Loomis

(Encyclopedia)Todd, Mabel Loomis, 1858–1932, American author, b. Cambridge, Mass. A friend of Emily Dickinson, she edited and deciphered much of the Dickinson material in Poems (with T. W. Higginson, Ser. 1 and S...

oscillator, electronic

(Encyclopedia)oscillator, electronic ŏsˈəlāˌtər [key], electronic circuit that produces an output signal of a specific frequency. An oscillator generally consists of an amplifier having part of its output ret...

modulation, in communications

(Encyclopedia)CE5 Modulation modulation, in communications, process in which some characteristic of a wave (the carrier wave) is made to vary in accordance with an information-bearing signal wave (the modulatin...

conjunction, in astronomy

(Encyclopedia)conjunction, in astronomy, alignment of two celestial bodies as seen from the earth. Conjunction of the moon and the planets is often determined by reference to the sun. When a body is in conjunction ...

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...