Question

A compound microscope has lenses of focal length 1cm and 3cm. An object is placed 1.2 cm from the object lens; if a virtual image is formed 25cm from the eye, calculate the separation of the lenses and the magnification of the instrument.

Answer 1

Answer

Imege distance can be calculated as

$v=\frac{uf_0}{u-f_0}=\frac{(1))( 1.2) }{1.2-1}\\v=6cm$

Object distance

$u^{'}=\frac{v^{'}f_e}{v^{'}-f_e}=\frac{(-25) (3) }{-25-3}=2.7cm$

Separation of lense=6+2.7=8.7cm

Magnification

$M=(\frac{D}{f_e}-1) \frac{v}{u}=(\frac{-25}{3}-1) \frac{6}{1.2}=-46.7$