UPSC CDS 1 2023 GK Paper

Concept:The power of a lens is the reciprocal of its focal length in metres.It measures the lens's ability to converge or diverge light.Power is expressed in dioptres (D).Explanation:The formula for power is $P = \frac{1}{f}$, where $f$ is the focal length in metres.Given focal length $f = 10$ cm.Convert centimetres to metres: $10$ cm $= 0.1$ m.Substitute into the formula: $P = \frac{1}{0.1} = 10$ D.Thus, the power of the lens is 10 dioptres.Answer:Option C – 10 dioptre.