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photoelectric cell
(Encyclopedia)CE5 Photoelectric cell: Light causes a photosensitive surface to emit electrons, which flow as current to the positive terminal. A galvanometer measures the current and thus indicates light intensi...telephone
(Encyclopedia)CE5 Hand telephone telephone, device for communicating sound, especially speech, usually by means of wires in an electric circuit. The telephones now in general use evolved from the device invente...oratory
(Encyclopedia)oratory, the art of swaying an audience by eloquent speech. In ancient Greece and Rome oratory was included under the term rhetoric, which meant the art of composing as well as delivering a speech. Or...cellular telephone
(Encyclopedia)cellular telephone or cellular radio, telecommunications system in which a portable or mobile radio transmitter and receiver, or “cellphone,” is linked via microwave radio frequencies to base tran...beryllium
(Encyclopedia)beryllium bərĭlˈēəm [key] [from beryl ], metallic chemical element; symbol Be; at. no. 4; at. wt. 9.01218; m.p. about 1,278℃; b.p. 2,970℃ (estimated); sp. gr. 1.85 at 20℃; valence +2. Ber...lever
(Encyclopedia)CE5 Classes of levers: A first-class lever (A), a second-class lever (B), and a third-class lever (C) lever, simple machine consisting of a bar supported at some stationary point along its length ...photographic processing
(Encyclopedia)photographic processing, set of procedures by which the latent, or invisible, image produced when a photographic film is exposed to light is made into a permanent visible image. The negative may b...space science
(Encyclopedia)space science, body of scientific knowledge as it relates to space exploration; it is sometimes also called astronautics. Space science draws on the conventional sciences of physics, chemistry, biolog...microscope
(Encyclopedia)CE5 Compound microscope microscope, optical instrument used to increase the apparent size of an object. The electron microscope, which is not limited by the powers of optical lenses and light,...Eakins, Thomas
(Encyclopedia)Eakins, Thomas āˈkĭnz [key], 1844–1916, American painter, photographer, and sculptor, b. Philadelphia, where he worked most of his life. Eakins is considered the foremost American portrait painte...Browse by Subject
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