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 phenomenon was first observed in crystals of tourmaline, the principal axis of which is a uniterminal triad axis of symmetry.

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

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

I also desired to have a rotation of nearly 180° about the principal axis.

From Scientific American Supplement, No. 365, December 30, 1882 by Various

By means of clockwork the instrument is given such a motion round its principal axis that the star is kept stationary in the field of view.

From The New Gresham Encyclopedia Volume 4, Part 2: Ebert to Estremadura by Various

To determine this ratio we consider its value for a vertex on the principal axis.

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