Write expression for the magnifying power of a simple microscope. How can it be increased ?

The magnifying power of a microscope is given by

$m=1+\frac{D}{f}$

where f is the focal length of the lens and D is the least distance of distinct vision for the normal eye.

The magnifying power of a microscope can be increased by using a lens of short focal length. But it cannot be increased indefinitely.