The various terms associated with spherical mirrors are:
1) Center of curvature:- The centre of curvature of a spherical mirror is the central point of the hallow sphere of which the mirror is a part.
2) Radius of curvature:- The radius of curvature of a spherical mirror is the radius of the hallow sphere of which the mirror is a part, in other words, it is the distance between the centre of curvature and pole of a mirror. It is represented by letter R.
3) Pole:- The pole of spherical mirror is the centre or middle point of a spherical mirror. It is represented by letter P.
4) Principle axis:- Principle axis of a spherical mirror is the line passing through the centre of curvature and its pole. In other words, it is the line joining the pole and centre of curvature of a mirror.
5) Secondary axis:- Any straight line other than the principal axis passing through the centre of a spherical mirror is referred to as secondary axis. It is usually represented by letters SS’ .
6) Aperture of a mirror:- Aperture of a mirror is the portion of a mirror from which reflection of light takes place. In other words it is the maximum size of a mirror. It is usually represented by letter M and M/ .