NEET 2025 · PhysicsPrevious Year Question
In a certain camera, a combination of four similar thin convex lenses are arranged axially in contact. Then the power of the combination and the total magnification, in comparison to the power (p) and magnification (m) for each lens, will be respectively:
- A.4p and m/4✓
- B.p/4 and m/4
- C.4p and 4m
- D.p/4 and 4m
Correct Answer
(A) 4p and m/4
Solution & Explanation
Answer: (A) 4p and m/4 Solution: For thin lenses in contact, powers add: P_total = p + p + p + p = 4p. Effective focal length F = 1/P_total = 1/(4p) = f/4 (where f = 1/p), i.e. one-quarter of a single lens's focal length. For the lens-equation magnification, a shorter combined focal length scales the magnification down; the net magnification of the combination is m/4. Hence: power = 4p and magnification = m/4.
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