![If an object is placed 21 cm from a converging lens, the image formed is slightly smaller](https://www.gkseries.com/blog/wp-content/uploads/2022/05/If-an-object-is-placed-21-cm-from-a-converging-lens-the-image-formed-is-slightly-smaller.png)
Q. 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 at a distance of 19 cm from the lens, the image formed is slightly larger than the object. The approximate focal length of the lens is:
A. 20 cm
B. 18 cm
C. 10 cm
D. 5 cm
Answer: 10 cm