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light

(Encyclopedia)light, visible electromagnetic radiation. Of the entire electromagnetic spectrum, the human eye is sensitive to only a tiny part, the part that is called light. The wavelengths of visible light range ...

photometry

(Encyclopedia)photometry fōtŏmˈətrē [key], 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...

Drummond light

(Encyclopedia)Drummond light: see calcium oxide. ...

light bulb

(Encyclopedia)light bulb: see lighting.

light horse

(Encyclopedia)light horse, any breed of horse that is used primarily for riding or for light work such as pulling buggies. Light horses have their origin in the Middle East and N Africa. All modern breeds of light ...

light-year

(Encyclopedia)light-year, in astronomy, unit of length equal to the distance light travels in one sidereal year. It is 9.461 × 1012 km (about 6 million million mi). Alpha Centauri and Proxima Centauri, the stars n...

black light

(Encyclopedia)black light: see ultraviolet radiation. ...

zodiacal light

(Encyclopedia)zodiacal light or zodiacal band, a faint band of light sometimes seen in the western sky just after sunset in the spring, extending up from the horizon at the point where the sun has just set, or in t...

Ibn al-Haytham

(Encyclopedia)Ibn al-Haytham ălhəzĕnˈ [key], 965–c.1040, Arab mathematician. Ibn al-Haytham was born in Basra, but made his career in Cairo, where he supported himself copying scientific manuscripts. Among hi...

electric-light bug

(Encyclopedia)electric-light bug: see water bug. ...