Q

A convex lens forms a real, inverted image three times the size of an object placed 30 cm from it. What is the approximate lens power?

RRB Group-D 11/08/2026 (12:45 PM - 2:15 PM) 2026
✓ Answer: A +4.44 D
m = -3 and u = -30 cm give v = +90 cm. Then 1/f = 1/90 + 1/30 = 2/45, so f = 22.5 cm = 0.225 m. P = 1/f ≈ +4.44 D.
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