Electron microscopes

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  • Created by: Steff06
  • Created on: 29-03-16 12:21
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  • Electron microscopes
    • Electron microscopes produce a beam of electrons which have a wavelength of 0.004nm.
    • Resolution of electron microscopes = 0.2nm
    • Electron microscopes use MAGNETS instead of lenses to focus the beam of electrons onto the specimen. Image produced from the beam is projected onto a screen to make a black and white image (electron micrographs).
    • TRANSMISSION electron microscope (TEM): Electron beam passes through a thin prepared sample. 2D image produced. Magnification possible = x500,000
    • SCANNING electron microscop (SEM): Beam is directed onto sample but does NOT pass through - they are 'bounced off'. 3D image produced. Magnification possible = x100,000
    • Advantages of electron microscopes:
      • Resolution = 0.2nm which is better than a light microscope.
      • Can be used to produce more DETAILED images of the organelles inside cells.
      • SEM produces 3D images that can reveal detail of tissue arrangements, which is not possible using  light microscope.
    • Disadvantages of electron microscopes:
      • Samples have to be placed in a VACUUM as electron beams are deflected by air molecules.
      • Electron microscopes are extremely EXPENSIVE.
      • Preparing samples and using an electron microscope require a high degree of SKILL and TRAINING.
    • Colour can be added after producing a final image using specialised computer software which will provide false colour.

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