A lens (positioned at x=1.5) and a lit object in the shape of an upright arrow is to the left by the lens. The object is positioned (x = 0.5) such that it results into a virtual image. The position of the virtual image is not given. A converging lens of focal length 0.7 can be added at x=2.5. The resulting image is at x=3.97.

a) Knowing that the focal length (df) is related to the object distance and the image distance (di) by this expression:

1/df = 1/do + 1/di

Find the do, the object distance for this second lens.

b) Now find the xo, the position of the object for this second lens.