To obtain a magnification of, -2 with a convex lens of focal length 10 cm, the object should be placed : (a) between 5 cm and 10 cm (h) between 10 cm and 20 cm (c) at 20 cm (d) beyond 20 cm
A 10 cm tall candle, when viewed using a convex lens appears to be 20 cm tall. The focal length is 5 cm. What is the object distance?