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refraction |
3 definitions found From Webster's Revised Unabridged Dictionary (1913) [web1913]: 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. 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 Refraction out of the rarer medium into the denser, is made towards the perpendicular. --Sir I. Newton. 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. {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. From Webster's Revised Unabridged Dictionary (1913) [web1913]: Angle \An"gle\ ([a^][ng]"g'l), n. [F. angle, L. angulus angle, corner; akin to uncus hook, Gr 'agky`los bent, crooked, angular, 'a`gkos a bend or hollow, AS angel hook, fish-hook, G. angel, and F. anchor.] 1. The inclosed space near the point where two lines meet a corner; a nook. Into the utmost angle of the world. --Spenser. To search the tenderest angles of the heart. --Milton. 2. (Geom.) a The figure made by two lines which meet b The difference of direction of two lines. In the lines meet the point of meeting is the vertex of the angle. 3. A projecting or sharp corner; an angular fragment. Though but an angle reached him of the stone. --Dryden. 4. (Astrol.) A name given to four of the twelve astrological ``houses.'' [Obs.] --Chaucer. 5. [AS. angel.] A fishhook; tackle for catching fish, consisting of a line hook, and bait, with or without a rod. Give me mine angle: we 'll to the river there --Shak. A fisher next his trembling angle bears. --Pope. {Acute angle}, one less than a right angle, or less than 90[deg]. {Adjacent} or {Contiguous angles}, such as have one leg common to both angles. {Alternate angles}. See {Alternate}. {Angle bar}. a (Carp.) An upright bar at the angle where two faces of a polygonal or bay window meet --Knight. b (Mach.) Same as {Angle iron}. {Angle bead} (Arch.), a bead worked on or fixed to the angle of any architectural work esp. for protecting an angle of a wall. {Angle brace}, {Angle tie} (Carp.), a brace across an interior angle of a wooden frame, forming the hypothenuse and securing the two side pieces together. --Knight. {Angle iron} (Mach.), a rolled bar or plate of iron having one or more angles, used for forming the corners, or connecting or sustaining the sides of an iron structure to which it is riveted. {Angle leaf} (Arch.), a detail in the form of a leaf, more or less conventionalized, used to decorate and sometimes to strengthen an angle. {Angle meter}, an instrument for measuring angles, esp. for ascertaining the dip of strata. {Angle shaft} (Arch.), an enriched angle bead, often having a capital or base, or both {Curvilineal angle}, one formed by two curved lines. {External angles}, angles formed by the sides of any right-lined figure, when the sides are produced or lengthened. {Facial angle}. See under {Facial}. {Internal angles}, those which are within any right-lined figure. {Mixtilineal angle}, one formed by a right line with a curved line {Oblique angle}, one acute or obtuse, in opposition to a right angle. {Obtuse angle}, one greater than a right angle, or more than 90[deg]. {Optic angle}. See under {Optic}. {Rectilineal} or {Right-lined angle}, one formed by two right lines. {Right angle}, one formed by a right line falling on another perpendicularly, or an angle of 90[deg] (measured by a quarter circle). {Solid angle}, the figure formed by the meeting of three or more plane angles at one point. {Spherical angle}, one made by the meeting of two arcs of great circles, which mutually cut one another on the surface of a globe or sphere. {Visual angle}, the angle formed by two rays of light, or two straight lines drawn from the extreme points of an object to the center of the eye. {For Angles of commutation}, {draught}, {incidence}, {reflection}, {refraction}, {position}, {repose}, {fraction}, see {Commutation}, {Draught}, {Incidence}, {Reflection}, {Refraction}, etc From WordNet r 1.6 [wn]: refraction n 1: the change in direction of a propagating wave (light or sound) when passing from one medium to another 2: the amount by which a propagating wave is bent [syn: {deflection}, {deflexion}]
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