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3 definitions found
 for Index of refraction
From The Collaborative International Dictionary of English v.0.48 :

  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 how much the economy has slowed.
        [1913 Webster +PJC]
              Tastes are the indexes of the different qualities of
              plants.                               --Arbuthnot.
        [1913 Webster]
     2. That which guides, points out, informs, or directs; a
        pointer or a hand that directs to anything, as the hand of
        a watch, a movable finger or other form of pointer on a
        gauge, scale, or other graduated instrument. In
        (printing), a sign [[hand]] (called also fist) used to
        direct particular attention to a note or paragraph.
        [1913 Webster]
     3. A table for facilitating reference to topics, names, and
        the like, in a book, usually giving the page on which a
        particular word or topic may be found; -- usually
        alphabetical in arrangement, and printed at the end of the
        volume. Typically found only in non-fiction books.
        [1913 Webster +PJC]
     4. A prologue indicating what follows. [Obs.] --Shak.
        [1913 Webster]
     5. (Anat.) The second finger, that next to the pollex
        (thumb), in the manus, or hand; the forefinger; index
        [1913 Webster]
     6. (Math.) The figure or letter which shows the power or root
        of a quantity; the exponent. [In this sense the plural is
        always indices.]
        [1913 Webster]
     7. The ratio, or formula expressing the ratio, of one
        dimension of a thing to another dimension; as, the
        vertical index of the cranium.
        [Webster 1913 Suppl.]
     8. A number providing a measure of some quantity derived by a
        formula, usually a form of averaging, from multiple
        quantities; -- used mostly in economics; as, the index of
        leading indicators; the index of industrial production;
        the consumer price index. See, for example, the consumer
        price index.
     9. (computers) A file containing a table with the addresses
        of data items, arranged for rapid and convenient search
        for the addresses.
     10. (computers) A number which serves as a label for a data
         item and also represents the address of a data item
         within a table or array.
     11. (R. C. Ch.), The Index prohibitorius, a catalogue of
         books which are forbidden by the church to be read; also
         called Index of forbidden books and Index Librorum
     Index error, the error in the reading of a mathematical
        instrument arising from the zero of the index not being in
        complete adjustment with that of the limb, or with its
        theoretically perfect position in the instrument; a
        correction to be applied to the instrument readings equal
        to the error of the zero adjustment.
     Index expurgatorius. [L.] See Index prohibitorius
     Index finger. See Index, 5.
     Index glass, the mirror on the index of a quadrant,
        sextant, etc.
     Index hand, the pointer or hand of a clock, watch, or other
        registering machine; a hand that points to something.
     Index of a logarithm (Math.), the integral part of the
        logarithm, and always one less than the number of integral
        figures in the given number. It is also called the
     Index of refraction, or Refractive index (Opt.), the
        number which expresses the ratio of the sine of the angle
        of incidence to the sine of the angle of refraction. Thus
        the index of refraction for sulphur is 2, because, when
        light passes out of air into sulphur, the sine of the
        angle of incidence is double the sine of the angle of
     Index plate, a graduated circular plate, or one with
        circular rows of holes differently spaced; used in
        machines for graduating circles, cutting gear teeth, etc.
     Index prohibitorius [L.], or Prohibitory index (R. C.
        Ch.), a catalogue of books which are forbidden by the
        church to be read; the index expurgatorius [L.], or
        expurgatory index, is a catalogue of books from which
        passages marked as against faith or morals must be removed
        before Catholics can read them. These catalogues are
        published with additions, from time to time, by the
        Congregation of the Index, composed of cardinals,
        theologians, etc., under the sanction of the pope. --Hook.
     Index rerum [L.], a tabulated and alphabetized notebook,
        for systematic preservation of items, quotations, etc.
        [1913 Webster]

From The Collaborative International Dictionary of English v.0.48 :

  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.
        [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
            [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
     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
     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
        [1913 Webster]

From WordNet (r) 3.0 (2006) :

  index of refraction
      n 1: the ratio of the velocity of light in a vacuum to that in a
           medium [syn: refractive index, index of refraction]

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