Answer to Question #102983 in Optics for Salo

Question

A microscope has an objective of focal length 0.3cm and an ocular of focal length 2.0cm. where must the image formed by the objective be for the ocular to produce a virtual image 25cm in front of the ocular?

Answer 1

As per the question,

Focal length of the objective lens $(f_o)$ =0.3cm

Focal length of the ocular lens $(f_2)$ =2.0cm

The distance of image for objective lens the lens $(u)=?$

The distance of the image by ocular lens (v)=25cm

So, $\dfrac{1}{f_2}=\dfrac{1}{v}-\dfrac{1}{u}$

$\dfrac{1}{u}=\dfrac{1}{2}+\dfrac{1}{25}$

$\dfrac{1}{u}=\dfrac{25+2}{50}=\dfrac{27}{50}$

$u=\dfrac{50}{27}=1.85cm$