A beam of electrons has a shorter wavelength than light so replacing the light beam in a microscope with an electron beam creates higher resolution (0.2nm). Magnets are used in place of lenses to focus and the reulting image is projected onto a screen or photographic paper forming a greyscale image called an electron micrograph.
Transmission Electron Microscope(TEM) - x500000 magnification, 2D image, electron beam travels through a thin prepared sample.
Scanning Electron Microscope(SEM)- x100000 magnification, 3D image, Electrons are bounced off the sample.
Advantages - resolution is 0.1nm, can produce images of organelles and cell structures, SEM can reveal contours or cellular/ tissue arrangements.
Limitations -Must be a vacuum, expensive, preparing samples require advanced training.
Specimens- fix the specimen, then dehydrate it, embed in a solid resin, cut thin slices with a diamond knife, stain with heavy metals to give contrast, mount on a copper grid.
Though electron micrographs are blank, white, and grey, computer software can give false-colour.
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