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eclipse

(Encyclopedia)eclipse klps´, – [key] [Gr.,=failing], in astronomy, partial or total obscuring of one celestial body by the shadow of another. Best known are the lunar eclipses, which occur when the earth b...

frequency

(Encyclopedia)frequency: see harmonic motion; wave.

Dyson, Sir Frank Watson

(Encyclopedia)Dyson, Sir Frank Watson d´sn [key], 1868–1939, English astronomer, b. Ashby-de-la-Zouch, grad. Cambridge. He was astronomer royal of Scotland (1905–10) and of England (from 1910). As director...

radio frequency

(Encyclopedia)radio frequency, range of electromagnetic waves with a frequency or wavelength suitable for communication uses. Some of these waves serve as carriers of the lower-frequency audio waves; others are mod...

frequency modulation

(Encyclopedia)frequency modulation: see modulation; radio.

audio frequency

(Encyclopedia)audio frequency: see sound; radio.

Freundlich, Erwin Finlay

(Encyclopedia)Freundlich, Erwin Finlay froind´lkh [key], 1885–1964, German astronomer. Freundlich obtained a doctorate in mathematics at Göttingen, then joined the Royal Observatory at Berlin, where he worked...

Algol

(Encyclopedia)Algol l´gl [key], famous variable star in the constellation Perseus; Bayer designation Persei; 1992 position R.A. 3h07.7m, Dec. +40°55. Algol's variation in apparent magnitude, from 2.06 t...

coronagraph

(Encyclopedia)coronagraph kr´ngrf [key], device invented by the French astronomer B. Lyot (1931) for the purpose of observing the corona of the sun and solar prominences occurring in the chromosphere. Be...

radio-frequency identification

(Encyclopedia)radio-frequency identification (RFID), a technology that uses radio waves to transmit data and uniquely identify an animal, person, or thing. An RFID system typically consists of a tag and a reader. T...