Question

which is called principal axis ?​

Answer 1

Answer:

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.

Answer 2

the line which passes through through pole or optical centre and focus in a mirror or Lens is called principal axis.

principal axis - a line that passes through the center of curvature of a lens so that light is neither reflected nor refracted