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Power of a lens is measured in:
AHertz
BNewtons
CWatts
DDioptres
Answer & Solution
Correct answer: D. Dioptres
1. The SI unit of power P = 1/f (in metres) is the dioptre (D).
2. One dioptre equals one inverse metre.
3. A converging lens has positive P; diverging lens negative.
_Source: NCERT Class 10 Science, Ch 9 "Light Reflection and Refraction", §9.4.4_
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