Magnification

http://www.msn.com/en-us/video/science/whats-the-smallest-thing-the-human-eye-can-see/vi-BBcKK2l

How lenses magnify
When you look through a magnifying glass, you are looking through a convex lens (one that’s bent like the back of a spoon on both sides) made of glass. The object being viewed is on the far side of the lens. Light from the object passes through the lens and is bent (refracted) towards your eye, so it seems as though it comes from a much bigger object.

Here is a magnified picture of a fly.  How does a convex lens magnify? A convex makes an image larger than the real object by bending the light rays coming from the object.



http://sciencelearn.org.nz/Contexts/Exploring-with-Microscopes/Science-Ideas-and-Concepts/How-microscopes-magnify