Question

Two converging lenses are separated by 24.60 cm. The focal length of each lens is 12.20 cm. An object is placed 35.40 cm to the left of the lens that is on the left. Determine the final image distance relative to the lens on the right.

Answer 1

The key to this kind of problem is that the 1st (left) lens's (intermediate) image is the 2nd (right) lens's object. Then we have, from ref. 1 (where +uN is object distance to left of lens and +vN is image distance to right of lens N):
u1 = 0.354 m: f1 = 0.122 m: f2 = 0.122 m; sep = 0.246 m
For the 1st lens:
v1 = 1 / (1/f1 -1/u1) = 0.354 m
For the 2nd lens:
u2 = sep - v1 = -0.108 m
v2 = 1 / (1/f2 - 1/u2) = 0.0573 m
The final image is 0.0573 + sep + 0.354 = 0.6573 m to right of object