Power of a lens (P) is defined as:
Af
B1/f (in meters; SI unit: dioptre)
C2/f
Df²
Answer & Solution
Correct answer: B. 1/f (in meters; SI unit: dioptre)
P = 1/f where f in meters. SI unit: dioptre (D). Convex lens: positive power; concave: negative. Doctors prescribe spectacles in dioptres.
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