principal axis

American  

noun

1. Optics. a line passing through the center of the surface of a lens or spherical mirror and through the centers of curvature of all segments of the lens or mirror.

2. Physics. one of three mutually perpendicular axes of a body about which the moment of inertia is maximum or minimum.

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principal axis British  

noun

1. the line passing through the optical centre and centres of curvature of the faces of a lens or a curved mirror

2. any of three mutually perpendicular axes about which the moment of inertia of a body is maximum

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Etymology

Origin of principal axis

First recorded in 1875–80

Example Sentences

This constant sum or difference equals in both cases the length of the principal axis.

From Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 6 "Geodesy" to "Geometry" by Various

The end surfaces and also the cut carried through the prism are parallel to the principal axis of the calc-spar.

From Scientific American Supplement, No. 441, June 14, 1884. by Various

The axis which contains the foci is called the principal axis; in case of an hyperbola it is the axis which cuts the curve, because the foci lie within the conic.

From Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 6 "Geodesy" to "Geometry" by Various

It is the parameter of the principal axis.

From The Gutenberg Webster's Unabridged Dictionary Section I, J, K, and L by Project Gutenberg

They will therefore cut the principal axis in two points, which are conjugate in the involution considered in � 84; hence they are harmonic conjugates with regard to the foci.

From Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 6 "Geodesy" to "Geometry" by Various