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Power of a convex lens of focal length 50 cm is:
A-2 D
B+2 D
C+5 D
D+0.5 D
Answer & Solution
Correct answer: B. +2 D
1. Power P = 1 / f, where f is in metres.
2. f = 50 cm = 0.5 m.
3. P = 1 / 0.5 = +2 dioptres.
4. The positive sign indicates a converging (convex) lens.
_Source: Selina Concise Physics ICSE Class 10, Ch 5 'Refraction through a Lens' (aplustopper.com extract)_
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