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, branch of physics dealing with the measurement of the intensity of a source of light, such as an electric lamp, and with the intensity of light such a source may cast on a surface area.
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The Columbia Electronic Encyclopedia™ Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/
A unit of light from one source. Light falling on 1 square foot of surface of an imaginary sphere having a 1-foot radius around 1 candle.
Illustrated Dictionary of Architecture Copyright © 2012, 2002, 1998 by The McGraw-Hill Companies, Inc. All rights reserved
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.
the unit of luminous flux in the International System of Units. Symbol, 1m. One lumen is the luminous flux emitted by an isotropic point source in a with a luminous intensity of 1 candela in a solid angle of 1 steradian.
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
The interior space within a tubular structure, such as within a blood vessel, a duct, or the intestine.
The unit of luminous flux, equal to the luminous flux emitted within a unit solid angle (1 steradian) from a point source having a uniform intensity of 1 candela, or to the luminous flux received on a unit surface, all points of which are at a unit distance from such a source. Symbolized lm.
(science and technology)
The space within a tube.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The SI unit of luminous flux equal to the luminous flux received on a unit surface, all points of which are equidistant from a point source having a uniform intensity of 1 candela.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.
lumenA unit of measurement of the light intensity radiating in the air in all directions from a light source. Lumens define "luminous flux," which is energy within the range of frequencies we perceive as light. For example, a wax candle generates about 13 lumens; a 60-watt bulb approximately 800, and a 100-watt bulb 1,600 lumens.
Lumen Ratings for Data Projectors
When choosing a data projector, the lumen rating is an important specification. In a small, dark room, 500 lumens may be ample; however, in a conference room with normal lighting, 1,000 to 2,000 lumens is required. In a large, well-lit room, at least 2,000 lumens is necessary. This rating is derived by taking the average of photometer readings at several points on a full white image on the screen. See lux, ANSI lumen, Lm/W, candela and spectrum.
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