[" Q47: "],[" If an object is placed "21cm" from a converging "],[" lens,the image formed is slightly smaller than the "],[" object.If the object is placed "19cm" from the lens,"],[" the image formed is slightly larger than object.The "]

If an object is placed 21 cm from a converging lens, the image formed is slightly smaller than the object. If the object is placed 19 cm from the lens, the image formed is slightly larger than the object. The approximate focal length of the lens is:

When the object is moved slightly closer to a converging lens, the image may