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

See Examples For:

principal axis

They are inclined to one another at equal oblique angles, and they are all equally inclined to the principal axis; further, they are all of equal length and are interchangeable.

From Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 7 "Crocoite" to "Cuba" by Various

The ends of the prism are perpendicular to its length; the section carried through it is in a plane perpendicular to the principal axis of the crystal.

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

The axis which contains the foci is called the principal axis, and the intersection of the axis with the curve is called the vertex of the curve.

From An Elementary Course in Synthetic Projective Geometry by Lehmer, Derrick Norman

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