Question

A laboratory (astronomical) telescope is used to view a scale that is 306 cm from the objective, which has a focal length of 20.0 cm; the eyepiece has a focal length of 2.40 cm. Calculate the angular magnification when the telescope is adjusted for minimum eyestrain. (Note: The object is not at infinity, and so the simple expression m = fo/fe is not sufficiently accurate for this problem. Also, assume small angles, so that tan(è) è.)