Two thin lenses of focal lengths f₁ and f₂ are in contact and co-axial. The power of the combination is:
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Question

Two thin lenses of focal lengths f₁ and f₂ are in contact and co-axial. The power of the combination is:

G1 Physics · Accepted Answer

Step 1: For contact lenses, 1/F = 1/f₁ + 1/f₂. Step 2: P = 1/F = (f₁ + f₂)/(f₁f₂) when focal lengths are in metres. Final answer: Source key (C). Check original printed options; two symbols are very faint in the scan.