College Physics 10th Edition by Raymond Serway,Chris Vuille

Exercise 63

Consider two thin lenses, one of focal length f 1 and the other of focal length f 2 , placed in contact with each other, as shown in Figure P23.56. Apply the thinlens equation to each of these lenses and combine the results to show that this combination of lenses behaves like a thin lens having a focal length f given by 1/ f = 1/ f 1 + 1/ f 2. Assume the thicknesses of the lenses can be ignored in comparison to the other distances involved.