You have a choice between two lenses of focal lengths f_a and f_b = 2 f_a to use as 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

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Quizplus · Accepted Answer

The magnification of a refracting telescope is given by:M = - (f_o / f_e)where f_o is the focal length of the objective lens and f_e is the focal length of the eyepiece lens.If we use lens A as the objective lens, then the magnification will be:M_a = - (f_a / f_e)If we use lens B as the objective lens, then the magnification will be:M_b = - (f_b / f_e)Substituting f_b = 2 f_a into the equation for M_b, we get:M_b = - (2 f_a / f_e)= -2 (f_a / f_e)= 2 M_aTherefore, the magnification when using lens B will be twice the magnification when using lens A.

You Have a Choice Between Two Lenses of Focal Lengths