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blueprint

(Encyclopedia)blueprint, white-on-blue photographic print, commonly of a working drawing used during building or manufacturing. The plan is first drawn to scale on a special paper or tracing cloth through which lig...

holography

(Encyclopedia)holography hŏlŏgˈrəfē, hō– [key], method of reproducing a three-dimensional image of an object by means of light wave patterns recorded on a photographic plate or film. Holography is sometimes...

color index

(Encyclopedia)color index, in astronomy, difference in an object's brightness as recorded between any two well-defined bands of the electromagnetic spectrum by using optical filters of different colors. If blue and...

Huygens, Christiaan

(Encyclopedia)Huygens, Christiaan krĭsˈtyän hoiˈgəns [key], 1629–95, Dutch mathematician and physicist; son of Constantijn Huygens. He improved telescopic lenses and discovered (1655) a satellite of Saturn a...

zinc oxide

(Encyclopedia)zinc oxide, chemical compound, ZnO, that is nearly insoluble in water but soluble in acids or alkalies. It occurs as white hexagonal crystals or a white powder commonly known as zinc white. Zinc white...

rum

(Encyclopedia)rum, spirituous liquor made from fermented sugarcane products. Prepared by fermentation, distillation, and aging, it is made from the molasses and foam that rise to the top of boiled sugarcane juice. ...

aberration of starlight

(Encyclopedia)aberration of starlight, displacement of the apparent path of light from a star, resulting in a displacement of the apparent position of the star from its true position; discovered by the English astr...

chiaroscuro

(Encyclopedia)chiaroscuro kyärōsko͞oˈrō [key] [Ital.,=light and dark], term once applied to an early method of printing woodcuts from several blocks and also to works in black and white or monotone. Today it i...

Finsen, Niels Ryberg

(Encyclopedia)Finsen, Niels Ryberg nēls rüˈbĕr fĭnˈsən [key], 1860–1904, Danish physician. He established in Copenhagen an institute of light therapy and wrote several books on his work. He received the 19...

lighthouse

(Encyclopedia)lighthouse, towerlike structure erected to give guidance and warning to ships and aircraft by either visible or radioelectrical means. Lighthouses were long built to conform in structure to their geog...