Question

The focal lengths of the objective and the eye-piece of a compound microscope are 1.0 cm and 2.5 cm respectively. Find the tube length of the microscope for obtaining a magnification of 300.

Answer 1

Given:

f_e = 2.5 cm, f_o = 1 cm

Let d be the minimum distance which should be kept away from an eye to see = 25 cm.

Magnification of compound microscope,

`m = m_o xx m_e`

`m = L/f_o xx D/f_e`

Here we need to find L (Length of the microscope), D = 25 cm (near point) and m = 300.

`300 = L/1 xx (25/2.5)`

L = 30 cm