extraordinary ray

noun

Optics, Crystallography.

1. the part of a doubly refracted ray that has changed speed and vibrations in the principal plane of the crystal.

extraordinary ray

noun

1. optics the plane-polarized ray of light that does not obey the laws of refraction in a doubly refracting crystal Compare double refraction ordinary ray

Word History and Origins

Origin of extraordinary ray¹

First recorded in 1870–75

Example Sentences

In “Fresnel’s ellipsoid” the axis of rotation is proportional to 587 the velocity of the extraordinary ray, and the equatorial diameters proportional to the velocity of the ordinary ray; it is therefore an oblate spheroid for positive crystals, and a prolate spheroid for negative crystals.

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Thus, in tourmaline the ordinary ray, which vibrates perpendicular to the principal axis, is almost completely absorbed, whilst the extraordinary ray is allowed to pass through the crystal.

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Huyghens explained, not only the laws of ordinary refraction in this manner, but, by supposing the secondary waves to form spheroids instead of spheres, he obtained the laws of refraction of the extraordinary ray in Iceland-spar.

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Optically, calcite is uniaxial with negative bi-refringence, the index of refraction for the ordinary ray being greater than for the extraordinary ray; for sodium-light the former is 1.6585 and the latter 1.4862.

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Or is he more liable to error in noting the fact of his mental joy or sorrow, than in observing the effect of the extraordinary ray in double refraction?

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