Microscopes

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  • Created by: emilyowl
  • Created on: 03-05-16 13:08

Transmission Electron Microscope

TRANSMISSION ELECTRON MICROSCOPE 

Consists of:

  • Electron gun - produces beam of electrons
  • Condenser electromagnet - focuses beam onto specimen
  • Screen - where image is shown and can be photographed (photomicrograph)

How image is seen:

  • Beam of electrons passes through thin section of specimen
  • Specimen absorbs electrons - appear dark
  • Electrons pass through specimen - appear bright

Limitations:

  • Vacuum required - can't observe living things 
  • Complex 'staining' process is needed
  • Extremely thin specimen 
  • Artefacts can be seen - things that are seen as a result of preparation
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Scanning Electron Microscope

SCANNING ELECTRON MICROSCOPE 

How image is seen:

  • Electrons do not penetrate
  • Beam of electrons directed onto surface from above 
  • Beam is passed back and forth in a regular pattern
  • Electrons are scattered 
  • Scattering depends on contours
  • A 3D image can be made on a computer

Limitations: 

  • Vacuum required - can't observe living things 
  • Complex 'staining' process is needed
  • Artefacts can be seen - things that are seen as a result of preparation
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