Question

The objective lens in a microscope with a 17.0 cm long tube has a magnification of -50.0 and the eyepiece has a magnification of 20.0. (a) What is the focal length of the objective? (b) What is the focal length of the eyepiece?

Answer 1

Answer:

(a) 0.34 cm

(b) 1.32 cm

Explanation:

Given that, $m_{o}=-50$

$m_{e}=20 cm$

And the length of objective lens in a microscope

$L=17$

And we have d of the eyepiece is 25 cm.

(a) Focal length of the objective is,

$f_{o}=-\frac{L}{m_{o} }\\ f_{o}=-\frac{17}{-50} \\f_{o}=0.34 cm$

Therefore, objective lens's focal length is 0.34 cm.

(b) Focal length of an eyepiece,

$m_{e}=(1+\frac{d}{f_{e} })\\ 20=(1+\frac{25}{f_{e} }\\ f_{e}=\frac{25}{19}cm\\ f_{e}=1.32cm$

Therefore, eyepiece's focal length is 1.32 cm.