Power of a lens of focal length 25 cm is

Power of a lens of focal length 25 cm is

+2-5 Dioptre
+3 Dioptre
+4 Dioptre
+5 Dioptre
This question was previously asked in
UPSC NDA-2 – 2021
The correct answer is C) +4 Dioptre.
The power of a lens (P) is defined as the reciprocal of its focal length (f), when the focal length is expressed in meters. The formula is P = 1/f.
Given focal length f = 25 cm. Convert this to meters: 25 cm = 0.25 m.
Power P = 1 / 0.25 m = 1 / (1/4) m = 4 Dioptre (D).
A positive power indicates a converging (convex) lens.