alleryPower of a concave lens is:
AAlways positive
BZero
CAlways negative
DInfinite
Answer & Solution
Correct answer: C. Always negative
1. Concave lens has a virtual focus on the same side as the object.
2. So focal length f is negative by sign convention.
3. Power P = 1 / f.
4. With f negative, P is also negative.
5. So a concave lens has negative power.
_Source: Selina Concise Physics ICSE Class 10, Ch 5 'Refraction through a Lens' (aplustopper.com extract)_
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