# longitude

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longitude
Refraction Re*frac"tion (r?*fr?k"sh?n), n. [F. r['e]fraction.] 1. The act of refracting, or the state of being refracted. [1913 Webster]

2. The change in the direction of ray of light, heat, or the like, when it enters obliquely a medium of a different density from that through which it has previously moved. [1913 Webster]

Refraction out of the rarer medium into the denser, is made towards the perpendicular. --Sir I. Newton. [1913 Webster]

3. (Astron.) (a) The change in the direction of a ray of light, and, consequently, in the apparent position of a heavenly body from which it emanates, arising from its passage through the earth's atmosphere; -- hence distinguished as atmospheric refraction, or astronomical refraction. (b) The correction which is to be deducted from the apparent altitude of a heavenly body on account of atmospheric refraction, in order to obtain the true altitude. [1913 Webster]

{Angle of refraction} (Opt.), the angle which a refracted ray makes with the perpendicular to the surface separating the two media traversed by the ray.

{Conical refraction} (Opt.), the refraction of a ray of light into an infinite number of rays, forming a hollow cone. This occurs when a ray of light is passed through crystals of some substances, under certain circumstances. Conical refraction is of two kinds; external conical refraction, in which the ray issues from the crystal in the form of a cone, the vertex of which is at the point of emergence; and internal conical refraction, in which the ray is changed into the form of a cone on entering the crystal, from which it issues in the form of a hollow cylinder. This singular phenomenon was first discovered by Sir W. R. Hamilton by mathematical reasoning alone, unaided by experiment.

{Differential refraction} (Astron.), the change of the apparent place of one object relative to a second object near it, due to refraction; also, the correction required to be made to the observed relative places of the two bodies.

{Double refraction} (Opt.), the refraction of light in two directions, which produces two distinct images. The power of double refraction is possessed by all crystals except those of the isometric system. A uniaxial crystal is said to be optically positive (like quartz), or optically negative (like calcite), or to have positive, or negative, double refraction, according as the optic axis is the axis of least or greatest elasticity for light; a biaxial crystal is similarly designated when the same relation holds for the acute bisectrix.

{Index of refraction}. See under {Index}.

{Refraction circle} (Opt.), an instrument provided with a graduated circle for the measurement of refraction.

{Refraction of latitude}, {longitude}, {declination}, {right ascension}, etc., the change in the apparent latitude, longitude, etc., of a heavenly body, due to the effect of atmospheric refraction.

{Terrestrial refraction}, the change in the apparent altitude of a distant point on or near the earth's surface, as the top of a mountain, arising from the passage of light from it to the eye through atmospheric strata of varying density. [1913 Webster]

The Collaborative International Dictionary of English. 2000.

Synonyms:

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• longitude — [ lɔ̃ʒityd ] n. f. • 1525; « longueur » 1314; lat. longitudo ♦ L une des coordonnées sphériques d un point de la surface terrestre; distance angulaire de ce point au méridien d origine mesurée en degrés. Île située par 60° de latitude sud et 40°… …   Encyclopédie Universelle

• Longitude — Lon gi*tude, n. [F., fr. L. longitudo, fr. longus long.] 1. Length; measure or distance along the longest line; distinguished from {breadth} or {thickness}; as, the longitude of a room; rare now, except in a humorous sense. Sir H. Wotton. [1913… …   The Collaborative International Dictionary of English

• longitude — Longitude. s. f. Terme d Astronomie & de Geographie. La distance du Couchant au Levant. On compte les degrez de longitude depuis le premier meridien. prendre les longitudes. ce lieu a tant de degrez de longitude, tant de latitude. ce seroit un… …   Dictionnaire de l'Académie française

• longitude — [län′jə to͞od΄, län′jətyo͞od΄; lôn′jə to͞od΄, lôn′jə tyo͞od΄] n. [ME < L longitudo < longus, LONG1] 1. length 2. distance east or west on the earth s surface, measured as an arc of the equator (in degrees up to 180° or by the difference in… …   English World dictionary

• longitude — late 14c., length, from L. longitudo length, duration, from longus (see LONG (Cf. long) (adj.)). For origins, see LATITUDE (Cf. latitude) …   Etymology dictionary

• longitude — s. f. 1. Distância de um ponto da terra ao meridiano geral. 2.  [Figurado] Distância, lonjura …   Dicionário da Língua Portuguesa

• longitude — The recommended pronunciation is lon ji tyood rather than long gi tyood. Beware of pronouncing it, let alone spelling it, longtitude …   Modern English usage

• longitude — Longitude, Longitudo …   Thresor de la langue françoyse

• longitude — ► NOUN ▪ the angular distance of a place east or west of a standard meridian, especially the Greenwich meridian. ORIGIN Latin longitudo, from longus long …   English terms dictionary

• Longitude — For Dava Sobel s book about John Harrison, see Longitude (book). For the adaptation of Sobel s book, see Longitude (TV series). Map of Earth Longitude (λ) Lines of longitude appear vertical with varying curvature in this projection, but are… …   Wikipedia

• Longitude — Les méridiens passent tous par les pôles La longitude est une coordonnée géographique représentée par une valeur angulaire, expression du positionnement est ouest d un point sur Terre (ou sur une autre planète). La longitude de référence sur… …   Wikipédia en Français