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phonon

(Encyclopedia)phonon fōˈnŏn [key], quantum of vibrational energy. The atoms of any crystal are in a state of vibration, their average kinetic energy being measured by the absolute temperature of the crystal. In ...

Dirac, Paul Adrien Maurice

(Encyclopedia)Dirac, Paul Adrien Maurice dĭrăkˈ [key], 1902–84, English physicist. He was educated at the Univ. of Bristol and St. John's College, Cambridge, and became professor of mathematics at Cambridge in...

superfluidity

(Encyclopedia)superfluidity, tendency of liquid helium below a temperature of 2.19K to flow freely, even upward, with little apparent friction. Helium becomes a liquid when it is cooled to 4.2K. Special methods...

Stefan, Josef

(Encyclopedia)Stefan, Josef yōˈzĕf shtĕfˈän [key], 1835–93, Austrian physicist. At the Univ. of Vienna he became a professor of physics and later director of the Physical Institute. From his observations on...

Lamb, Willis Eugene, Jr.

(Encyclopedia)Lamb, Willis Eugene, Jr., 1913–2008, American physicist, b. Los Angeles, Ph.D. Univ. of California, Berkeley, 1938. Lamb was a professor at Columbia (1938–51), Stanford (1951–56), Oxford (1956�...

energy

(Encyclopedia)CE5 Relations between potential energy (PE) and kinetic energy (KE) for a swinging pendulum energy, in physics, the ability or capacity to do work or to produce change. Forms of energy include hea...

Soddy, Frederick

(Encyclopedia)Soddy, Frederick sŏdˈē [key], 1877–1956, English chemist. He worked under Lord Rutherford at McGill Univ. and with Sir William Ramsay at the Univ. of London. After serving (1910–14) as lecturer...

Broglie, Louis Victor, duc de

(Encyclopedia)Broglie, Louis Victor, duc de, 1892–1987, French physicist. In 1928 he became professor in the faculty of sciences, Univ. of Paris. It was known from the earlier quantum theory that light waves some...

energy, sources of

(Encyclopedia)energy, sources of, origins of the power used for transportation, for heat and light in dwelling and working areas, and for the manufacture of goods of all kinds, among other applications. The develop...

photoelectric effect

(Encyclopedia)photoelectric effect, emission of electrons by substances, especially metals, when light falls on their surfaces. The effect was discovered by H. R. Hertz in 1887. The failure of the classical theory ...