Electron microscopes

In a microscope light of a certain wavelength is used which, by a series of lenses, provides a magnified picture of an object. There exists a fundamental limit ot the resolving power of a microscope, however, due to diffraction effects. Recall that significant diffraction occurs when light of a certain wavelength is shone through an opening whose width is comparable to the wavelength of the light. When used in a microscope, therefore, one would want to avoid diffraction effects, as this scatters the light which dulls the image. What this means is that a microscope which uses light of a certain wavelength can ``see'' objects only as small as the wavelength of the light being used. For microscopes that use visible light this size is therefore of the order of 10<sup>-6</sup> m, while X-ray machines can see scales down to about 10<sup>-10</sup> m. One can though make electron microscopes which use electron waves as the ``light'' source; such microscopes can see objects as small as about 10^-12 m or even smaller, providing at least an order of magnitude improvement over X-rays.