CALCULATION OF THE FOCAL LENGTH OF A TWO-LENS SYSTEM - AN EDUCATIONAL EXPERIMENT.

In the present work, an educational experiment is presented for the estimation of the focal lengths of the individual lenses that compose a two-lens system. The method is based on the measurement of the back focal length and the equivalent focal length of the two-lens system. The experimental setup is simple, two convex lenses of equal focal lengths are positioned at a distance d and by measuring the back focal length of the two-lens system the unknown focal lengths are derived. In addition, the image size observed by the two-lens system is compared to that of different single test lenses in order to derive the equivalent focal length. The experimental methodology is straightforward and provides all the important information that can be obtained for a two-lens system in a geometrical optics laboratory, without expensive equipment. [ABSTRACT FROM AUTHOR]