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Doppler effect

(Encyclopedia)Doppler effect, change in the wavelength (or frequency) of energy in the form of waves, e.g., sound or light, as a result of motion of either the source or the receiver of the waves; the effect is nam...

X-ray astronomy

(Encyclopedia)X-ray astronomy, study of celestial objects by means of the X rays they emit, in the wavelength range from 0.01 to 10 nanometers. X-ray astronomy dates to 1949 with the discovery that the sun emits X ...

Heaviside, Oliver

(Encyclopedia)Heaviside, Oliver hĕvˈēsīdˌ [key], 1850–1925, English physicist. He did valuable work in telephony and in the theory of electrical conduction in cables and other areas of electric theory. He su...

Braun, Karl Ferdinand

(Encyclopedia)Braun, Karl Ferdinand broun [key], 1850–1918, German physicist. Braun taught at the Univ. of Marburg, Strasbourg Univ., Karlsruhe's Technische Hochschule, and the Univ. of Tübingen before being na...

Bloch, Felix

(Encyclopedia)Bloch, Felix, 1905–83, American physicist, b. Zürich, Switzerland, Ph.D. Univ. of Leipzig, Germany, 1928. He was a professor at Stanford from 1934 until his retirement in 1971. Bloch and Edward Pur...

Munk, Walter Heinrich

(Encyclopedia)Munk, Walter Heinrich, 1917–2019, American oceanographer and geophysicist, b. Vienna (then in Austria-Hungary), B.S. California Institute of Technology, 1939, Ph.D Univ. of California, Los Angeles, ...

Purcell, Edward Mills

(Encyclopedia)Purcell, Edward Mills, 1912–97, American physicist, b. Taylorville, Ill., Ph.D. Harvard, 1938. During World War II, Purcell was a researcher at the Massachusetts Institute of Technology Radiation La...

De Forest, Lee

(Encyclopedia)De Forest, Lee, 1873–1961, American inventor, b. Council Bluffs, Iowa, grad. Yale, 1896. He was a pioneer in the development of wireless telegraphy, sound pictures, and television. His triode (1906)...

echo, in acoustics

(Encyclopedia)echo, reflection of a sound wave back to its source in sufficient strength and with a sufficient time lag to be separately distinguished. If a sound wave returns within 1⁄10 sec, the human ear is in...

broadcasting

(Encyclopedia)broadcasting, transmission, usually using radio frequencies, of sound or images to a large number of radio or television receivers. In the United States the first regularly scheduled radio broadcasts ...