Two point surces `S_(1) and S_(2)` are 24 cm apart. Where should a convex lens of focal length 9 cm be placed them , so that the images of both sources are formed at the same place ?

Explanation

In this case one of the image will be real and the other virtual. Let us assume that image of `S_1` is real and that of `S_2` is virtual
Applying `1/y+1/x=1/9`
For `S_1,1/y+1/x=1/9…..(1) S_2:1/y+1/(24-x)=1/9`……….(2)
Solving eqs. (1) and (2) we get x=6cm