optic axis

American  

noun

Crystallography.

1. (in a crystal exhibiting double refraction) the direction or directions, uniaxial or biaxial, respectively, along which this phenomenon does not occur.

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optic axis British  

noun

1. the direction in a uniaxial crystal or one of the two directions in a biaxial crystal along which a ray of unpolarized light may pass without undergoing double refraction

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Etymology

Origin of optic axis

First recorded in 1655–65

Example Sentences

A surface expressing the optical relations of such crystals is thus an ellipsoid of revolution about the optic axis.

From Project Gutenberg

The source of light—the filament of a Nernst lamp—was moved about in a plane 120 cm. distant from the eye and perpendicular to the optic axis.

From Project Gutenberg

In the oceanic Decapoda the cornea does not completely close, but leaves a central aperture traversed by the optic axis.

From Project Gutenberg

But this, I am convinced, was a mere delusion, for all rays of light falling in the direction of the optic axis must have been intercepted and reflected by the opaque capsule.

From Project Gutenberg

This direction of no double refraction is called the optic axis of the crystal.

From Project Gutenberg