PHYS102: Introduction to Electromagnetism

In a microscope, we guide light rays emitted from two very closely spaced points on the object (for example a microorganism) so they converge back together in two spots on the retina that are spaced much farther apart than on the object itself. That allows our eye to distinguish the two points clearly, and as a result we can see details that would have been completely washed out for the unaided eye.

Watch this lecture, which draws the ray diagrams that explain this.