Q110 / 270 · NDA 2018 (Phase 2) · General Ability

If the focal length of a convex lens is 50 cm , which one of the following is its power?

Correct answer
A
+2 dioptre
B
+0.02 dioptre
C
-0.5 dioptre
D
+0.5 dioptre

Solution

Power of a lens is always reciprocal to the focal length. So, a convex lens with 50 cm focal length has a power of (1/0.5) Dioptre (D) or 2D. Since, a convex lens is a converging lens, the power of the convex lens is +2 D .

Hence, the correct answer is option: 'A'.

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