Chapter-9|Ray Optics and Optical Instrument|NCERT 12th Physics:
Microscope is an optical instrument which form large image of close and minute objects.
A simple microscope is a converging lens of small focal length.
When an object is at a distance less than the focal length of the lens, the image obtained in virtual, erect and magnified.
When the object is at a distance equal to the focal length of the lens, the image is formed at infinity.
Case1: When the image is formed at the near point.