Question

The line joining the pole and the centre of curvature of a spherical mirror is called the:

Options

• Normal

• Tangent

• Radius of curvature at the point of incidence

• Principal axis

Answer 1

The principal axis of a spherical mirror is defined as the straight line joining the pole (the geometric centre of the mirror) and the centre of curvature. A normal, by contrast, is the radius drawn to the point of incidence, not the line from the pole to the centre of curvature.