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Serving or having power to refract, or turn from a direct course; pertaining to refraction; as, refractive surfaces; refractive powers. Refractive index. (Opt.) See Index of refraction, under Index. -- Absolute refractive index (Opt.), the index of refraction of a substances when the ray passes into it from a vacuum.…

A contrivance for exhibiting and measuring the refraction of light.

A refracting telescope, in which the image to be viewed is formed by the refraction of light in passing through a convex lens.

Full; complete; not broken; not fractional; approximately in even units, tens, hundreds, thousands, etc.; -- said of numbers. Pliny put a round number near the truth, rather than the fraction. Arbuthnot.

bar of wood, ivory, metal, or the like, which is usually marked so as to show inches and fractions of an inch, and jointed so that it may be folded compactly. A judicious artist will use his eye, but he will trust only to his rule. South.

Paper fractional currency. [Colloq.U.S.]

The decimal point; the dot placed at the left of a decimal fraction, to separate it from the whole number which it follows. The term is sometimes also applied to other marks of separation.

The quotient of a unit divided by seventy; one of seventy equal parts or fractions.

Pertaining to, or founded on, the number sixty. Sexagesimal fractions or numbers (Arith. & Alg.), those fractions whose denominators are some power of sixty; as, astronomical fractions, because formerly there were no others used in astronomical calculations. -- Sexagesimal, or Sexagenary, arithmetic, the method of com…

Toward the side; sidewise. A second refraction made sideways. Sir I. Newton. His beard, a good palm's length, at least, . . . Shot sideways, like a swallow's wings. Longfellow.

t event. Significant figures (Arith.), the figures which remain to any number, or decimal fraction, after the ciphers at the right or left are canceled. Thus, the significant figures of 25,000, or of .0025, are 25.

The several colored and other rays of which light is composed, separated by the refraction of a prism or other means, and observed or studied either as spread out on a screen, by direct vision, by photography, or otherwise. See Illust. of Light, and Spectroscope.

ose from points of view a little way apart. It is furnished with two eyeglasses, and by refraction or reflection the pictures are superimposed, so as to appear as one to the observer.

, to indicate its time or meter. Also called rhythmical signature. It is in the form of a fraction, of which the denominator indicates the kind of note taken as time unit for the beat, and the numerator, the number of these to the measure.

as in the air waves constituting sound, but transversely, and the various phenomena of refraction, polarization, interference, etc., are attributable to the different affections of these undulations in different circumstances of propagation. It is computed that the frequency of the undulations corresponding to the sev…

Having but one optic axis, or line of no double refraction.

Duodecimal unit, a unit in the scale of numbers increasing or decreasing by twelves. -- Fractional unit, the unit of a fraction; the reciprocal of the denominator; thus, unit of the fraction -- Integral unit, the unit of integral numbers, or 1. -- Physical unit, a value or magnitude conventionally adopted as a unit…

a. & n. from Vanish, v. Vanishing fraction (Math.), a fraction which reduces to the form Math. Dict. -- Vanishing line (Persp.), the intersection of the parallel of any original plane and picture; one of the lines converging to the vanishing point. -- Vanishing point (Persp.), the point to which all parallel lines in…

ocus (Opt.), the point from which rays, having been rendered divergent by reflection of refraction, appear to issue; the point at which converging rays would meet if not reflected or refracted before they reach it. -- Virtual image. (Optics) See under Image. -- Virtual moment (of a force) (Mech.), the product of the…

men, minds, language, or manners. Be thou familiar, but by no means vulgar. Shak. Vulgar fraction. (Arith.) See under Fraction.