A laser beam of diameter d1 = 1.1 mm is directed along the optical axis of a thin lens of focal length +6.0 cm (see figure below).
1) How far from the lens will the beam be focused?
2) A second positive lens is placed to the right of the first. Light emerges from the second lens in a parallel beam of diameter d2 = 3.9 mm. Thus the combination of lenses acts as a beam expander. Find the focal length of the second lens.
3) Find the distance between the lenses.
