|MadSci Network: Microbiology|
Even the best light microscopes can only resolve objects to a size around 200nm= 2/10,000,000 of a meter. This is about the size of mitochondria, or small bacteria. The electron microscope, however, is able to resolve objects to about 200pm= .2nm= 2/10,000,000,000 of a meter. That is only a 1000 fold improvement on the light microscope, but enough to make a big difference. Electron microscopy is really the only existing method of viewing objects as small as viruses. Bacterial viruses average about 10-50nm in diameter, while animal and plant viruses average about 50-300nm. You'll notice that the upper size of animal and plant viruses are at about the absolute resolving ability of the regular light microscope. The resolving power of a microscope is inversely proportional to the wavelength of the radiation source used to view the object(remember that light is a part of the elctromagnetic radiation spectrum. The visible spectrum of light ranges in wavelength from about 380nm(violet light) to 750nm(red). So if we use a radiation source that has very large wavelengths, such as visible light, our absolute resolving power isn't that great compared to a source with much smaller wavelengths, such as electrons(about 2pm= .002nm). With a microscope of either type, when you magnify the object more and more, you lose resolution. So even though the light microscope can resolve down to 200nm, it isn't really that clear. So we have to turn to the electron microscope. As for building your own devise that would allow you to view a virus better than an electron microscope, it will be pretty tough. You'll have to find a radiation source that has a very small wavelength, and doesn't destroy your sample. The smaller you get in wavelength, there is higher energy, and that creates damage. Gamma rays have a very small wavelength, but create a lot of damage to biological molecules, especially DNA. But if you find a way pull it off, you'll be famous! Good luck. Mark Sullivan
Try the links in the MadSci Library for more information on Microbiology.