Answer: +5 D
Power of a lens is the reciprocal of its focal length in metres: \(P = \dfrac{1}{f}\).
\[f = 20\ \text{cm} = 0.2\ \text{m}, \qquad P = \frac{1}{0.2} = +5\ \text{D}\]
The power is positive because a convex lens is a converging lens.
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Doubtly AI
· 25 Oct 2026
AI-verified · Oct 2026
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