microscopy

• define magnification


  the number of times greater an image is compared to the actual object being viewed
• define resolution


  the degree to which it is possible to distinguish between two points that are close together
• total magnification 


  eyepiece lens magnification x objective lens magnification
• types of microscopes:

  • optical microscope
  • SEM
  • TEM
  • laser scanning
• optical microscope

  • uses visible light
  • cheap + portable
  • can be used on living cells
  • low magnification and resolution
• laser scanning

  • uses different coloured lasers
  • builds 3D image in great detail
  • can be used on living tissue
  • expensive
• scanning electron microscope

  • scans beam of electrons across the specimen
  • looks at the surface of specimen only
  • costly/no colour produced
  • specimen must be dead due to vacuum
  • high resolution/magnification
• transmission electron microscope

  • electromagnets focus a beam of electrons through specimen
  • internal structures can be viewed
  • dead specimens specially prepared
  • very costly + need training