Question

Which of the following (referred to a spherical mirror) do (does) not depend on whether the rays are paraxial or not?
(a) Pole
(b) Focus
(c) Radius of curvature
(d) Principal axis

Answer 1

(a) Pole
(c) Radius of curvature
(d) Principal axis

Paraxial rays are the light rays close to the principal axis. The focus of the spherical mirror for paraxial rays are different from the focus for marginal rays. So, the focus depends on whether the rays are paraxial or marginal. ​The pole, radius of curvature and the principal axis of a spherical mirror do not depend on paraxial or marginal rays.