Q. A person with a normal near point (25cm) using a compound microscope with objective of focal length 8.0mmandan eye piece of focal length 2.5cm can bring an object placed at 9.0mm from the objective in sharp focus. What is the separation between the two lenses? Calculate the magnifying power of the microscope.

Answer

A Focal length of the objective lens f o=8mm=0.8cm

A Focal length of the eye piece f e=2.5cm

An Object distance for the objective lens u o=-9.0mm=-0.9cm

The Least distance of distant vision d=25cm

An Image distance for the eyepiece ve=-d=-25cm

An Object distance for the eyepiece=μ_e

Utilizing the lens formula we can obtain the value of μ_e as

We can as  well obtain the value of the image distance for the objective lens v₀ using the lens formula.

The distance among the objective lens and the eyepiece =|u_e|+v₀

=2.27+7.2

=9.47 cm

A magnifying power of the microscope is calculated as:

Thus the magnifying power of the microscope is 88.