Define (a) centre of curvature, (b) radius of curvature, (c) pole, (d)princip[al axis.

a) Centre of curvature: Center of curvature of a spherical mirror is the center of the hollow sphere of a glass of which the mirror is a part.

(b) Radius of curvature: Radius of curvature of a spherical mirror is the radius of the hollow sphere of glass of which the mirror is a part.

(c) Pole: The center of a spherical mirror is called its pole.

(d) Principal axis: The straight line passing through the centre of curvature and pole of a spherical mirror is called its principal axis.

(e) Aperture: The portion of a mirror from which the reflection of light actually takes place is called Aperture.

All the term have been defined.