Question

An object is placed 40 cm from a convex lens of focal length 30 cm. If a concave lens of focal length 50 cm is introduced btw the convex lens and the image formed such that it is 20 cm from the convex lens, find the change on the position of the image.

Answer 1

Dear Student ,
Here in this case image formed by the convex lens acts as the virtual objet for the concave lens .
$$\begin{gathered} Sofromlensmakersformula,weget, \\ \frac{1}{v}-\frac{1}{u}=\frac{1}{f} \\ \Rightarrow \frac{1}{v}-\frac{1}{10}=-\frac{1}{50} \\ \Rightarrow v=12·5cm=dis\tan ceofthenewimagefromtheconcavelens. \end{gathered}$$

Regards