Question

Two thin lenses are in contact and object is placed at 60cm from the lens. It forms a real image at a distance of 35cm from the lens. one of the lenses is converging with the focal.length of 20cm.complete or determine the nature and the total length of the second lens.

Answer 1

$\frac{1}{F_1}+\frac{1}{F_2}=\frac 1 f+\frac 1d,$

$F_1=20,~d=60,~f=35,\implies$

$F_2=-210~cm,$ concave.