Index of refraction
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.

Look at other dictionaries:

  • Index of refraction — Index In dex, n.; pl. E. {Indexes}, L. {Indices}(?). [L.: cf. F. index. See {Indicate}, {Diction}.] [1913 Webster] 1. That which points out; that which shows, indicates, manifests, or discloses; as, the increasing unemployment rate is an index of …   The Collaborative International Dictionary of English

  • index of refraction — n. the ratio of the sine of the angle of incidence to the sine of the angle of refraction for a ray of light crossing from one medium into another …   English World dictionary

  • index of refraction — n the ratio of the speed of radiation (as light) in one medium (as a vacuum) to that in another medium called also refractive index …   Medical dictionary

  • index of refraction — noun the ratio of the velocity of light in a vacuum to that in a medium • Syn: ↑refractive index • Hypernyms: ↑ratio * * * : the ratio of the velocity of light or other radiation in the first of two media to its velocity in the second as it… …   Useful english dictionary

  • index of refraction — Optics. a number indicating the speed of light in a given medium as either the ratio of the speed of light in a vacuum to that in the given medium (absolute index of refraction) or the ratio of the speed of light in a specified medium to that in… …   Universalium

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  • Index Of Refraction —    This is the measure of the refracting power of a transparent substance. It is the ratio of the speed of light in a vacuum compared to the speed of light as it passes through the transparent substance. See Invisible and Refraction …   The writer's dictionary of science fiction, fantasy, horror and mythology

  • index of refraction — Date: 1829 refractive index …   New Collegiate Dictionary

  • index of refraction — noun → refractive index …   Australian English dictionary

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