Question

Name the line that acts as normal to the spherical mirror at its pole ​

Answer 1

This imaginary line is called the principal axis or optical axis of the mirror. Any line through the center of curvature of a sphere is an axis of symmetry for the sphere, but only one of these is a line of symmetry for the spherical cap. The adjective "principal" is used because its the most important of all possible axes.

Answer 2

Answer:

Imagine a straight line passing through the pole and the centre of curvature of a spherical mirror. This line is called the principal axis. Remember that principal axis is normal to the mirror at its pole.