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laser

(Encyclopedia)CE5 Ordinary light sources produce incoherent light, while a laser produces a beam of coherent light. laser [acronym for light amplification by stimulated emission of radiation], device for the cr...

airglow

(Encyclopedia)airglow, faint diffuse illumination of the sky originating in the upper atmosphere. Although it occurs at all times of day throughout the upper atmosphere, it is most typically visible to an observer ...

gallium

(Encyclopedia)gallium gălˈēəm [key], metallic chemical element; symbol Ga; at. no. 31; at. wt. 69.723; m.p. 29.78℃; b.p. 2,403℃; sp. gr. 5.904 at 29.6℃ (solid), 6.095 at 29.8℃ (liquid); valence +2 or +3...

cosmic rays

(Encyclopedia)cosmic rays, charged particles moving at nearly the speed of light reaching the earth from outer space. Primary cosmic rays consist mostly of protons (nuclei of hydrogen atoms), some alpha particles (...

night blindness

(Encyclopedia)night blindness, inability to see normally in subdued light. It is usually a result of vitamin A deficiency. The rod cells, one of two light-sensitive areas of the retina of the eye, are impaired in t...

Beattie, James

(Encyclopedia)Beattie, James, 1735–1803, Scottish poet and essayist. Educated at Marischal College, Aberdeen, he later became professor of moral philosophy there. His fame in his own lifetime rested on two works,...

Bedford, John of Lancaster, duke of

(Encyclopedia)Bedford, John of Lancaster, duke of, 1389–1435, English nobleman; third son of Henry IV of England and brother of Henry V. At the death (1422) of his brother and succession of his 9-month-old nephew...

York, Edmund of Langley, duke of

(Encyclopedia)York, Edmund of Langley, duke of, 1341–1402, fifth son of Edward III of England. He was made (1362) earl of Cambridge, served on expeditions to Spain and France, and married (1372) Isabel, daughter ...

Gloucester, Thomas of Woodstock, duke of

(Encyclopedia)Gloucester, Thomas of Woodstock, duke of, 1355–97, English nobleman; youngest son of Edward III. He was betrothed (1374) to Eleanor, heiress of Humphrey de Bohun, earl of Hereford, and became earl o...

albedo

(Encyclopedia)albedo ălbēˈdō [key], reflectivity of the surface of a planet, moon, asteroid, or other celestial body that does not shine by its own light. Albedo is measured as the fraction of incident light th...