In a two-lens system, the image produced by one lens acts as the object for the next lens. This simple principle finds applications in many optical instruments, including some of common use such as the microscope and the telescope. On one of the shelves in your physics lab is displayed an antique telescope. A sign underneath the instrument says that the telescope has a magnification of 20 and consists of two converging lenses, the objective and the eyepiece, fixed at either end of a tube 60.0 cm long. Assuming that this telescope would allow an observer to view a lunar crater in focus with a completely relaxed eye, what is the focal length (fe) of the eyepiece?

In a two-lens system, the image produced by one lens acts as the object for the next lens. This simple principle finds applications in many optical instruments, including some of common use such as the microscope and the telescope. On one of the shelves in your physics lab is displayed an antique telescope. A sign underneath the instrument says that the telescope has a magnification of 20 and consists of two converging lenses, the objective and the eyepiece, fixed at either end of a tube 60.0 cm long. Assuming that this telescope would allow an observer to view a lunar crater in focus with a completely relaxed eye, what is the focal length (fe) of the eyepiece?