Doubling the focal length of the objective lens of a compound microscope will change the magnification by what factor?
A)1/4
B)1/2
C)2
D)4

Question

Quizplus · Accepted Answer

According to the formula for magnification of a compound microscope, M = -(fo/fp)(L/fe), where fo is the focal length of the objective lens, fp is the focal length of the eyepiece, L is the length of the tube, and fe is the least distance of distinct vision. When the focal length of the objective lens is doubled (fo becomes 2fo), the magnification becomes M' = -(2fo/fp)(L/fe) = 2M. Therefore, the magnification is doubled, which corresponds to a factor of 2. Hence the correct choice is B, which represents doubling the original magnification.

Doubling the Focal Length of the Objective Lens of a Compound