Compound Microscope

A Laboratory Model of Compound Microscope

It is an optical instrument used for observing highly magnified images of tiny objects.

O - Objective

E - Eyepiece

D - Distance of distinct vision

AB - Object

A'B' - First image

A"B" - Final image

O₁,O₂ - are optic centers of O and E

O, F_O - Focal length of objective

O, F_e - Focal length of eyepiece

Magnifying power of compound microscope is defined as the ratio of the angle subtended at the eye by the final image to the angle subtended at the eye by the object, when both the final image and the object are situated at the least distance of distant vision from the eye.

m = magnification produced x magnification produced due to eye lens due to objective lens

m = m_e x m_o

(-ve sign shows that final image is inverted with respect to the object)

Note:

If the object is very close to f_o, the focus of lens O then

and as A^lB^l is very close to the eye lens

V_o = O_lB^l O₁O₂ = L = length of tube

If f_o and f_e both are small then magnifying power will be large.