Question

What is principal axis ?​

Answer 1

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• An optical axis is a line along which there is some degree of rotational symmetry in an optical system such as a camera lens, microscope or telescopic sight. The optical axis is an imaginary line that defines the path along which light propagates through the system, up to first approximation.

Answer 2

English -> each of three mutually perpendicular axes in a body about which the moment of inertia is at a maximum.

Hindi-> मुख्य धुरी।