Electron Microscopy

In the early 1930s, the German physicist Ernst Ruska and his assistant, an electrical engineer called Mark Knoll took advantage of the de Broglie hypothesis leading to the development of the first electron microscope in Germany, probably the single most important development in microbiology. Immensely contributing to the field, electron microscopy has and continues to provide new insights on cellular activity and spatial organization within different cellular compartments.

With a wavelength 1,000 times shorter than violet light, greater magnification and finer resolution can be achieved by using an electron beam than electromagnetic fields. The resolution of electron microscopes is on the order of 5-50 nm, ten times larger than atomic sizes and down to 1 angstrom with the FEI Titan transmission electron microscope!

In a transmission electron microscope (TEM) an electron beam is directed onto a very thin sample (10 nm ~ 100 atoms thick). Differing numbers of electrons pass through the sample, depending on its structure, to ultimately generate a highly magnified silhouette image of the sample. Due to the inability of the eye to generate an image from an electron beam, the microscope generates a real image which is projected onto either photographic film, a CCD detector or onto a fluorescent screen which can be viewed by the human eye under a binocular eyepiece. The general components of an electron microscope are analogous to that of  an optical microscope. An electron microscope uses magnetic lenses rather than glass lenses to focus and manipulate the electron beam. The whole apparatus is housed in a high vacuum environment to prevent the electrons colliding with gas molecules

The surfaces of thicker 3D objects such as cells, tissues, bugs and flowers can be studied using a scanning electron microscope (SEM).

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