Visible electromagnetic wave energy in the spectrum range from 3,800 to 7,200 angstrom units, a measurement of light waves. Longer wavelength is infrared light, and that of shorter wavelength is ultraviolet light. It is the natural agent that stimulates the sense of sight and is measured by candle, foot-candle, and lumen. It spreads equally in all directions at once over large areas, and diminishes in intensity according to the square of the distance from the source. Light is usually measured in terms of luminous flux. When light hits a surface, it will either be absorbed, reflected, transmitted, or refracted. Also, an opening through which daylight is admitted to the interior space of a building; an individual pane of glass, window, or compartment of a window.
Illustrated Dictionary of Architecture Copyright © 2012, 2002, 1998 by The McGraw-Hill Companies, Inc. All rights reserved