Two converging lenses with the focal lengths f 1 = 0.2 m and f2 = 0.4 m are positioned at a distance f1 + f2 to each other. such arrangements are called "beam expanders" and are often used in laser technology
a) what is the expansion ratio w2 / w1?
one of the two converging lenses is now to be replaced by a diverging lens, with the same expansion ratio w2 / w1 to be achieved.
b) which of the two lenses is that and what is the focal length of the dissipation lens?
c) what is the distance of the lenses now?