Print ThisHow Does a Microscope Work?
Anton van Leeuwenhoek
Public Domain
A Bit of History
Just as Galileo didn’t invent the telescope, Anton van Leeuwenhoek didn’t invent the microscope. Yet, just as Galileo discovered an unknown universe of the very large when he pointed his telescope upward, Leeuwenhoek discovered an unknown universe of the very small when he used the microscope to look where no one had before.
Leeuwenhoek examined the microscopic world, discovering tiny animals, plants, and bacteria in a drop of water. He studied blood cells and how they move, even exploring the life cycles of insects. Because of his pioneering work, Leeuwenhoek is often called “the father of microscopy”.
How It Works
A microscope uses the same trick as a refracting telescope — light waves being bent as they travel through glass. In a telescope, the idea is to bend parallel light from very faraway objects into a small focus at the eye. In a microscope, the idea is to bend diverging (spreading-out) light into a parallel path, then bend that parallel-path light into a small focus at the eye.
Light enters the bottom, travels through the objective lenses and then through the eyepiece lenses.
by David Garrison
To make a little more sense of that, let’s try to magnify something. Maybe it’s a dust mite, a tiny bug that lives in your pillow and eats your dead skin (ew!).
First, we have to light up the dust mite. A mirror mounted under the microscope stand does the job. Light bounces off the mirror, passes through and around our dust mite (mounted firmly to a microscope slide), and into the objective lenses. These lenses bend some of the spread-out light beams from the dust mite into straight line paths that travel through the microscope tube. Next, the light beams reach the eyepiece lenses. These lenses bend the light back into your eye, so you can see the dust mite up close and personal.
The power of the microscope depends on how much each lens bends the light. Usually, the power is written right on the microscope itself. 40x, for instance, means that the image at the eyepiece is 40 times larger than real life.
Microscope Facts
Most microscopes use more than one lens for the objective and the eyepiece. This helps prevent a problem called “chromatic aberration”. While it’s true that light is bent as it passes through glass, it’s also true that some colours are bent more than others. The multiple lenses in the objective and the eyepiece help to correct that problem.
This micrograph (photograph made with a microscope) shows the round green chloroplasts inside plant cells.
by Nancy Nehring
Your body (and the bodies of all other living things) is made from tiny units called cells. No one knew this until Robert Hooke used a microscope to look at slices of cork. Cork (a type of wood) has very pronounced cell walls that make the cork look like it’s made of lots of very small rooms, or cells.
Different types of microscopes have been used to look at human cells, identify minerals, solve crimes, see how freezing affects food, study metals, and find the causes of crop diseases. Microscopes are an essential tool in medicine too. They have been used to identify the causes of many deadly diseases like malaria and tuberculosis. Microscopes can also help to find out why a person or animal died.
Scientists can even use a microscope to figure out where illegal drugs come from. For example, looking at opium crystals through a microscope reveals different shapes depending on where the poppies they came from were grown. This information can help pinpoint the source of illegal drugs.
Food For Thought
Just as astronomers use things other than visible light to study the heavens, other scientists use things other than light to study the microscopic world. One of those things is the electron. A device called the electron microscope can “see” objects like atoms that we could never make out with visible light.
This insect has been coated in gold so it can be viewed with a scanning electron microscope.
Just like a beam of light, a beam of electrons can be bent. Unlike light, though, electrons aren’t bent by glass lenses. Instead, electron beams are bent by magnets. The objects “viewed” by a scanning electron microscope have to be electrical conductors, and they have to be able to withstand a vacuum. To help with both these requirements, subjects for study in an electron microscope are often coated with a thin layer of gold.
Of course, you don’t need an electron microscope (or even a pot of gold) to make some amazing discoveries. Even a simple, low-power microscope can open up a new world. Try looking at plants, paper, cloth, sugar, pond water, even the odd flea. Lots of aquarium supply stores sell tiny shrimp, called brine shrimp, which are really interesting to look at through a microscope. The possibilities for what you can find out with a microscope are endless. And who knows, you might identify something new and it may even get named after you!
For Further Information
The Ultimate Guide to Your Microscope by Shar Levine and Leslie Johnstone (2008). This book includes lots of ideas for what to examine and instructions for preparing your own microscope samples.
Looking at Microscopes by Peter D. Riley (1985). Short, basic introduction to different types of microscopes and their uses.
Experimenting With a Microscope by Maurice Bleifeld (1988). Beginner’s guide to using a microscope including looking at plants, animals, and everyday objects.
The Complete Beginner's Guide to Microscopes and Telescopes by Aaron E. Klein (1980). This book offers some tips about what to look for when buying a microscope, hints about using your microscope, and some of the things you can examine under a microscope (organisms that live in pond water, your own cells, pollen, plants, cloth, yeast).
Microscopes and Magnifying Lenses by Janice VanCleave (1993). Subtitled “Mind-boggling Chemistry and Biology Experiments You Can Turn Into Science Fair Projects”, this book covers 20 topics that you can explore even if you don't have a microscope.