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Question
Define the following terms in the context of spherical mirrors :
(i) Pole
(ii) Centre of curvature
(iii) Radius of curvature
(iv) Principal axis
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Solution

(i) Pole of a spherical mirror
The central point of the reflecting surface of a spherical mirror is termed as the pole. It lies on the mirror and is denoted by the letter (P).
(ii) Centre of curvature
The centre of curvature is the centre of a sphere from which the given spherical mirror (convex or concave) is obtained. It is denoted by the letter (C).
(iii) Radius of curvature
The distance between the centre of curvature and pole (PC) is known as the radius of curvature.
(iv) Principal axis
The imaginary straight line joining the pole (P) and the centre of curvature (C) is termed as the principal axis.
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