refraction : Idioms & Phrases

noun the angle between a refracted ray and a line perpendicular to the surface between the two media at the point of refraction

(Opt.), the angle which a refracted ray makes with the perpendicular to the surface separating the two media traversed by the ray.

(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.

(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.

noun splitting a ray into two parallel rays polarized perpendicularly
birefringence.

. (Opt.) See 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.

a species of double image micrometer, in which the two images are formed by the double refraction of rock crystal.

noun the ratio of the velocity of light in a vacuum to that in a medium
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 refraction.

(Opt.), the plane in which lie both the incident ray and the refracted or reflected ray.

(Opt.), an instrument provided with a graduated circle for the measurement of refraction.

etc., the change in the apparent latitude, longitude, etc., of a heavenly body, due to the effect of atmospheric 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.