Question

An object is to be seen through a simple microscope of focal length 12 cm. Where should the object be placed so as to produce maximum angular magnification? The least distance for clear vision is 25 cm.

Answer 1

For the given simple microscope,

f = 12 cm and d = 25 cm

For maximum angular magnification, the image should be produced at least distance of clear vision.

v = D = -25 cm

Now, $\frac{1}{v}-\frac{1}{u}=\frac{1}{f}$

$\Rightarrow \frac{1}{v}=\frac{1}{u}+\frac{1}{f}$

$=\frac{1}{-25}=\frac{1}{12}$

$=-\frac{25+12}{300}=-\frac{37}{300}$

$\Rightarrow U=-\frac{300}{37}=-8.1cm$

So the object should be placed at 8.1 cm away from the lens.