Question

An angular magnification (magnifying power) of 30X is desired using an objective of focal length 1.25 cm and an eyepiece of focal length 5 cm. How will you set up the compound microscope?

Answer 1

Focal length of the objective lens,f_o= 1.25 cm 

Focal length of the eyepiece, fe = 5 cm

Least distance of distinct vision, d = 25 cm 

Angular magnification of the compound microscope = 30X

Total magnifying power of the compound microscope, m = 30

The angular magnification of the eyepiece is given by the relation:

The angular magnification of the objective lens (mo) is related to me as:

Applying the lens formula for the objective lens:

The object should be placed 1.5 cm away from the objective lens to obtain the desired magnification. 

Applying the lens formula for the eyepiece:

Therefore, the separation between the objective lens and the eyepiece should be 11.67 cm.