A burning candle whose flame is 1.5 cm tall is placed at a certain distance in front of a convex lens. An image of candle flame is received on a white screen kept behind the lens. The image of flame also measures 1.5 cm. If f is the focal length of convex lens, the candle is placed:

A convex lens of focal length 8 cm forms a real image of the same size as the object. The distance between object and its image will be:

A virtual, erect and magnified image of an object is to be obtained with a convex lens. For this purpose, the object should be placed:

A lens of focal length 15 cm forms an erect image three times the size of the object. The distance between the object and image is:

(a) 20 cm (b) 16 cm

(c) 24 cm (d) 36 cm

If an object is placed 23 cm from a converging lens, the image formed is slightly smaller than the object. If the object is placed 21 cm from the lens, the image formed is slightly larger than the object. The approximate focal length of the lens is:

(a) 11 cm (b) 10 cm

(c) 18 cm (d) 20 cm