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

The directrix is at right angles to the principal axis.

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

It is the parameter of the principal axis.

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

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

Benzoic acid is pseudo-tetragonal, the principal axis being remarkably long; there is no cleavage at right angles to this axis.

From Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 1 "Châtelet" to "Chicago" by Various

It will be seen from the figure how the principal axis of the instrument rests upon the two masonry pillars, one of which is 49 ft. and the other 13 ft. in height.

From Scientific American Supplement, No. 803, May 23, 1891 by Various