A lens has power −2.5 D. It is a
A. convex lens of focal length 40 cm
B. concave lens of focal length 25 cm
C. concave lens of focal length 40 cm
D. convex lens of focal length 2.5 m
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Answer: C. concave lens of focal length 40 cm
\(f = \frac{1}{P} = \frac{1}{-2.5} = -0.4\) m \(= -40\) cm. A negative power means a concave lens.
Doubtly AI
· 24 Oct 2026
AI-verified · Oct 2026
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