Question

3) Define principal axis of a spherical lens​

Answer 1

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

Answer 2

Answer:

The straight line passing through the geometrical centre of a lens and joining the two centres of curvature of its surfaces. Sometimes the optical axis of a lens is called its principal axis.