Q

A student observes that when an object is placed at 15 cm from a mirror, the image is formed at 30 cm on the same side. What is the focal length of the mirror?

RRB Group D 13 Aug, 2026 (12:45 PM - 2:15 PM) 2026
✓ Answer: A -10 cm
The correct choice is -10 cm. It follows from the laws of reflection/refraction and the standard image-formation properties of lenses, mirrors or optical systems.
← Previous Question Next Question →

📚 Related Questions — Light

1 A student notices that the image formed by a lens is virtual,… 2 Which of the following statements is FALSE for a converging lens? 3 A student observes that the image formed by a lens is twice… 4 A car driver uses a rear-view mirror to observe vehicles behind. If… 5 A convex lens forms a real, inverted image three times larger than… 6 A traffic surveillance camera uses a convex mirror with a radius of…