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,= 1.25 cm

Focal length of the eyepiece, f_e = 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 (m_o) is related to m_e as:

= m

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:

Where,

= Image distance for the eyepiece = −d = −25 cm

= Object distance for the eyepiece

Separation between the objective lens and the eyepiece

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