(a) Define (i) principal focus of a concave mirror, and (ii) focal length of a concave mirror.(b) Draw diagram to represent the action of a concave mirror on a beam of parallel light rays. Mark on this diagram principal axis, focus F, centre of curvature C, pole P and focal length f, of the concave mirror.
(a) Definitions-
(i) Principal focus $(F)$ of a concave mirror: It is the point on its principal axis to which all the light rays which are parallel and close to the principal axis, converge after getting reflected from the concave mirror.
(ii) Focal length $(f)$: It is the distance between its principal focus $(F)$ and pole $(P)$.
(b) Ray Diagram-
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