Biology, Answering the Big Questions of Life/Microscopes
How do we see things that are very small?
In order to see things that are smaller than the eye can see, we use tools called microscopes. Light can be bent by pieces of glass called lenses, and this is how magnifying glasses are made that make images look bigger.
A magnifying glass is a simple microscope. If you place one magnifying glass over another one, you can make an image appear larger than it appears with only one magnifying glass. A microscope that uses two or more lenses to magnify an image is called a compound microscope.
Types of Microscopes
Compound light microscopes
Biologists today have many types of microscopes that they use to observe cells, but the most commonly used is the compound light microscope. A compound light microscope uses light bent by glass lenses to magnify a thin sample of something. Living cells can be observed with a compound light microscope.
An electron microscope can see objects smaller than cells such as details inside bacterial cells, and the structures of large proteins and viruses. Most samples must be killed (fixed) before they can be observed by an electron microscope. An electron microscope uses electrons instead of light to view an image. This gives an image with a higher resolution.
A transmission electron microscope shines electrons straight through a sample just as a compound light microscope shines light through a sample. A scanning electron microscope bounces electrons off of the surface of sample. Both types of microscope view the image projected on a surface like a television screen.
Proximity probe microscopes
A proximity probe microscope uses a very sharp probe that glides across the surface of a sample. The image is composited by a computer. Proximity probe microscopes vary by the type of probe, and by what it measures. Some proximity probe microscopes can detect individual atoms and molecules.
An atomic force microscope is a type of proximity probe microscope that moves across the surface of an object like a blind person reading in braille. It tilts up and down due to the atomic forces of the surface below, and this can be measured to make an image.