The correct relation between the radius of curvature R and focal lengt

The correct relation between the radius of curvature R and focal length f of a spherical mirror is

R = f

R = 2f

R = 3f

R = 4f

Answer is Right!

Answer is Wrong!

This question was previously asked in

UPSC NDA-2 – 2020

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The correct answer is B) R = 2f.

For a spherical mirror (concave or convex) with a small aperture, the focal length (f) is defined as half of its radius of curvature (R). This fundamental relationship is expressed as f = R/2 or R = 2f.

The radius of curvature (R) is the radius of the sphere from which the mirror is a part, and the focal length (f) is the distance from the mirror’s pole to its principal focus (the point where parallel rays converge after reflection for a concave mirror, or appear to diverge from for a convex mirror). This relationship holds true for paraxial rays, i.e., rays close to and parallel to the principal axis.

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