Q

A real, inverted image forms 30 cm in front of a concave mirror when the object is 60 cm from it. What is the focal length?

RRB Group-D 21/08/2026 (4:30 PM - 6:00 PM) 2026
✓ Answer: A -20 cm
1/f = 1/(-60) + 1/(-30) = -1/20, giving f = -20 cm.
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