An object is kept at a distance of `16 cm` from a thin lens and the image formed is real. If the object is kept at a distance of `6 cm` from the lens, the image formed is virtual. If the sizes of the images formed are equal, the focal length of the lens will be

Options

A. 19 cm
B. 17 cm
C. 21 cm
D. 11 cm

Answer

D

Explanation

(d) Lens should be convex. Images should be magnified by focal length 16 cm length should lie between f and 2f.
Because corresponding to 6 cm (`gt`f) length image should be magnified.
from the given options, if f = 11 cm.
Then, 6 cm, `gt` f and 11 cm`gt` 16 cm `gt` 22 cm or f`gt`16 cm `gt` 2f