Question

You are given two converging lenses of focal lengths 1.25 cm and 5 cm to design a compound microscope. If it is desired to have a magnification of 30, find out the separation between the objective and the eyepiece.

a) 2.5 cm
b) 3.5 cm
c) 4.5 cm
d) 5.5 cm

Answer 1

The separation between the objective and the eyepiece is 6.25 cm. (Option D).

How to calculate the separation between the objective and the eyepiece?

The separation between the objective and the eyepiece is calculated by applying the following formula as shown below.

Magnification of compound microscope;

M = -L/f₀ (1 + d/fe)

where;

• d is a constant and equal to the normal distance of clear vision of the human eye = 26
• f₀ the focal length of the objective lens = 1.25 cm
• fe is the focal length of the eyepiece = 5 cm

-30 = -L/1.25 (1 + 25/5)

30 = L/1.25 (1 + 5)

1.25(30) = L(6)

L = (1.25 x 30 ) / 6

L = 6.25 cm

Thus, the closest option is 5.5 cm.