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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 ...

Sacks, Oliver Wolf

(Encyclopedia)Sacks, Oliver Wolf, 1933–2015, British neurologist and author, b. London, educated at Queen's College, Oxford. In 1960 he moved to the United States, where he continued his medical training. He bega...

Hohenzollern, German princely family

(Encyclopedia)Hohenzollern hōˌən-tsôlˈərn [key], German princely family that ruled Brandenburg (1415–1918), Prussia (1525–1918), and Germany (1871–1918). Originating in S Germany and traceable to the 11...

Dampier, William

(Encyclopedia)Dampier, William dămˈpēr [key], 1651–1715, English explorer, buccaneer, hydrographer, and naturalist. He fought (1673) in the Dutch War, managed a plantation in Jamaica (1674), and then worked wi...

dark energy

(Encyclopedia)dark energy, repulsive force that opposes the self-attraction of matter (see gravitation) and causes the expansion of the universe to accelerate. The search for dark energy was triggered by the discov...

Maastricht

(Encyclopedia)Maastricht mäsˈtrĭkhtˌ [key], city (1994 pop. 118,102), capital of Limburg prov., SE Netherlands, on the Maas (Meuse) River and on the Albert Canal system. It is an important rail and river transp...

Boleyn, Anne

(Encyclopedia)Boleyn, Anne bo͝olˈĭn, bo͝olĭnˈ [key], 1507?–1536, second queen consort of Henry VIII and mother of Elizabeth I. She was the daughter of Sir Thomas Boleyn, later earl of Wiltshire and Ormonde,...

berkelium

(Encyclopedia)berkelium bûrˈklēəm [key] [from Berkeley], artificially produced radioactive chemical element; symbol Bk; at. no. 97; mass no. of most stable isotope 247; m.p. about 1,050℃; b.p. about 2,590℃;...

Planck, Max

(Encyclopedia)Planck, Max mäks plängk [key], 1858–1947, German physicist. Seeking to explain the experimental spectrum (distribution of electromagnetic energy according to wavelength) of blackbody radiation, he...

Danton, Georges Jacques

(Encyclopedia)Danton, Georges Jacques zhōrzh zhäk däNtôNˈ [key], 1759–94, French statesman, one of the leading figures of the French Revolution. A Parisian lawyer, he became a leader of the Cordeliers early ...