alleryIf the focal length of a convex lens is doubled, its power:
ADoubles
BHalves
CStays the same
DBecomes zero
Answer & Solution
Correct answer: B. Halves
1. Power P = 1 / f.
2. Doubling f means f becomes 2f.
3. New P = 1 / (2f) = (1/f) / 2.
4. So the new power is half the original.
5. Hence power halves.
_Source: Selina Concise Physics ICSE Class 10, Ch 5 'Refraction through a Lens' (aplustopper.com extract)_
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