Convex lens use – Microscope
The difference between a magnifying glass and a microscope is that a magnifying glass is made with one lens while a microscope is made from a combination of lenses. They usually call a microscope a compound microscope because it combines lenses. A lens that uses two or more lenses is called a compound lens.
Each lens magnifies only once, so each one increases the size of the image a bit more. Compound microscopes can magnify an extremely small object such as microorganisms which is naked to a human eye or even a magnifying glass and make details visible.
A magnifying glass may magnify an object 2X but a compound microscope can achieve far more than 200X.
See the ray diagram below:
The early compound microscopes were built illustrated below:
The mirror was used to bring light into the microscope to light up the tiny object.
Modern microscopes use many more lenses and methods to create a very focused image.
The light under the object is designed to transmit light through a translucent object for viewing.