Q

A convex lens forms a real, inverted image three times larger than the object. If the object is placed 30 cm from the lens, what is the closest approximate value of the power of the lens?

RRB Group D 11 Aug, 2026 (12:45 PM - 2:15 PM) 2026
✓ Answer: A +4.44 D
For a real image three times the size, m = −3, so v = 90 cm for u = −30 cm. The lens formula gives f = 22.5 cm, hence P ≈ 1/0.225 = +4.44 D.
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