Magnifying glass as simple Microscope:






1) When the object is in between the focal length & the optical centre, the magnifying power of the lens is





This magnifying power can be proved as follows









Suppose v = D now according to sign 
convention v = - D So





These measurement can be seen from below



 





2)


When the object is at the focus of the lens, the magnifying power of the lens is



Where D is the best clear distance or maximum closest distance for an eye, that you can see an image clearly.



Normally D = 25 cm