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or heat, falls on any surface. In equal incidences there is a considerable inequality of refractions. Sir I. Newton. Angle of incidence, the angle which a ray of light, or the line of incidence of a body, falling on any surface, makes with a perpendicular to that surface; also formerly, the complement of this angle.…

integral figures in the given number. It is also called the characteristic. -- 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 o…

r future. (b) (Navigation) Tables for correcting an observed lunar distance on account of refraction and parallax. -- Lunar year, the period of twelve lunar months, or 354 days, 8 hours, 48 minutes, and 34.38 seconds.

the instrument is large and equatorially mounted, it is known as a heliometer. -- Double refraction micrometer, a species of double image micrometer, in which the two images are formed by the double refraction of rock crystal. -- Filar, or Bifilar, micrometer. See under Bifilar. -- Micrometer caliper or gauge (Mech.…

tomaine) formed in the decomposition of protagon with boiling baryta water, and in the putrefraction of proteid matter. It was for a long time considered identical with choline, a crystalline body originally obtained from bile. Chemically, however, choline is oxyethyl-trimethyl-ammonium hydroxide, while neurine is viny…

ly seen. (b) The line in a doubly refracting crystal, in the direction of which no double refraction occurs. A uniaxial crystal has one such line, a biaxial crystal has two. -- Optical circle (Opt.), a graduated circle used for the measurement of angles in optical experiments. -- Optical square, a surveyor's instrume…

ded circular polarization of light. -- Optically positive, Optically negative. See under Refraction.

re referred for the purpose of determining their relative position in space. -- Plane of refraction or reflection (Opt.), the plane in which lie both the incident ray and the refracted or reflected ray.

sic radicals. Positive crystals (Opt.), a doubly refracting crystal in which the index of refraction for the extraordinary ray is greater than for the ordinary ray, and the former is refracted nearer to the axis than the latter, as quartz and ice; -- opposed to negative crystal, or one in which this characteristic is r…

or sides, and two equal and parallel triangular ends or bases; -- used in experiments on refraction, dispersion, etc.

lors of the spectrum, and formed in the part of the hemisphere opposite to the sun by the refraction and reflection of the sun's rays in drops of falling rain.

ys, below. -- Extraordinary ray (Opt.), that one or two parts of a ray divided by double refraction which does not follow the ordinary law of refraction. -- Ordinary ray (Opt.) that one of the two parts of a ray divided by double refraction which follows the usual or ordinary law of refraction. -- Pencil of rays (Ge…

Turned from a direct course by refraction; as, refracted rays of light.

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.

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.

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.

rpose 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.

n, 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 s…