
Given here: Focal length of convex lens, f=10cm
Now, as seen in figure, image from lens is formed at point I1, whose location is 5cm from mirror. Thus, I1 is at 15cm from lens.
Using lens equation, we have
v1−u1=f1
Putting the value,
151−−u1=101
⇒u1=101−151⇒u=10−1510×15
Thus, object is placed at 30cm from lens.
