Q

A convex lens forms a real, inverted image of an object placed at a distance of 30 cm from the lens. The image is found to be formed at a distance of 60 cm on the other side of the lens. What is the focal length of the lens?

RRB Group D 13 Aug, 2026 (4:30 PM - 6:00 PM) 2026
✓ Answer: C 20 cm
The correct choice is 20 cm. It follows from the laws of reflection/refraction and the standard image-formation properties of lenses, mirrors or optical systems.
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