You have a choice between two lenses of focal lengths f_a and f_b,where f_b = 2f_a,to use as the objective lens in building a refracting telescope.If the magnification you obtain using lens a is M_a,what will be the magnification when using lens b? A)M_b = 2 M_a B)M_b = 4 M_a C)M_b = 8 M_a D)M_b = M_a/4 E)M_b = M_a/2

Question

Quizplus · Accepted Answer

The magnification of a refracting telescope is given by:M = -f_o/f_ewhere f_o is the focal length of the objective lens and f_e is the focal length of the eyepiece lens.In this case, we have two objective lenses with focal lengths f_a and f_b, where f_b = 2f_a. If the magnification obtained using lens a is M_a, then the magnification obtained using lens b will be:M_b = -f_b/f_e = -2f_a/f_e = 2M_aTherefore, the correct answer is A) M_b = 2 M_a.

You Have a Choice Between Two Lenses of Focal Lengths