With the help of a suitable diagram, explain the meaning of the following terms for a concave mirror.
(a) centre of curvature
(c) principal axis
(a) Centre of curvature: It is the centre of the sphere of which the spherical mirror is a part.
(b) Pole: It is the central point of a spherical mirror.
(c) Principal axis: it is the line joining the pole of the mirror and its centre of curvature.
(d) Focus: The point, on the principal axis, where all the rays, incident parallel to the principal axis, actually meet, or appear to meet, after their reflection by the spherical mirror is called focus of that mirror.