Physicshard · Past Paper
Two thin lenses of focal lengths 20 cm and 25 cm are placed in contact. The effective power of the combination is:
A9 D
B45 D
C5 D
D1 D
✓ Correct Answer: A — 9 D
P1 = 1/0.2 = 5D, P2 = 1/0.25 = 4D. Total P = 5 + 4 = 9D.
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