Microscopy

• Electron microscopes

  • TEM - transmission electron microscope
  • SEM - scanning electron microscope
• Light microscope

  • magnification - x1500
  • resolution - 0.2 µm
• TEM microscope

  • magnification - x1,000,000
  • resolution - 0.0002 µm
• SEM microscope

  • magnification - x500,000
  • resolution - 0.002 µm
• SEM microscope

  • electron beam causes electrons from sample to get knocked off, they are received by a cathode
  • once processed, 3D images produced
• TEM microscope

  • electrons are transmitted through the specimen, some are absorbed
  • once processed, 2D image produced
• electron microscopes

  • specimens must be dead
  • black and white images only - can be coloured after
  • can be stained by using heavy metal ions
• light microscopes

  • specimens can be alive or dead
  • images are colourful
  • can be stained using chemicals
• TEM images

  • 2D image
  • light background
  • dark specimen
• SEM images

  • 3D image
  • dark background
  • lighter specimen
• Magnification 


  The number of times larger an image is than the actual object
• Resolution


  The ability to distinguish separate points on an image as two separate objects
• Light microscopes

  • able to observe whole cells and tissues
• Transmission electron microscope

  • electrons transmitted through the specimen - 2D images
  • to observe organelles - cell interior and ultrastructure
  • black and white images
  • greater magnification and greater resolution
• Scanning electron microscope

  • electrons are knocked off of the specimen and are received - 3D images
  • to observe a cells surface
  • black and white images
  • lower magnification and lower resolution