In a light microscope (LM), visible light is passed through the specimen and then through glass lenses. The lenses refract (bend) the light so that the image of the specimen is magnified. Light microscopes were first used by Renaissance scientists and are still widely used in biology.
Some important parameters in microscopy are magnification and resolution. Magnification is the ratio of an object's image size to its real size. Resolution is a measure of the clarity of an object. Another important parameter is contrast, which accentuates differences in parts of the sample.
The light microscope has a limited resolving power; it cannot resolve detail finer than .2 micrometers, or the size of a small bacterium.
- Campbell, Neil A., and Jane B. Reece. Biology. San Francisco: Benjamin Cummings, 2002.