Methods of studying cells

• What is the eyepiece graticule for?

  Measuring the size of cells or objects
• what are the unit’s of the eyepiece graticule

  Not a specific scale but measured in eyepiece units (e.p.u)
• What are the pros of using light microscopes

  • can be used to observe living things
  • Inexpensive
  • specimen can be viewed in colour
  • can be used to view larger organelles
• What are the cons of using a light microscope

  • low resolution - cannot see ribosomes so they cannot see objects smaller than 0.2 micrometres
  • Limited magnification
• Pros of using an electron microscope

  • high resolution and magnification
  • Able to view smaller structures like the ribosomes and Golgi apparatus
  • 3D imagery when using a scanning electron microscope
• Cons of using an electron microscope

  • can only be used on non-living specimens
  • Preparation of samples can be complex (slicing into very thin sections or coating with metal)
  • the electron beam can damage the specimen over time
  • Expensive
  • Requires training to use
  • Black and white images produced
• Magnification =

  Image size/actual size
• What are transmission electron microscopes

  Uses a high energy beam of electrons that passes through a very thin specimen
• What are scanning electron microscopes

  Images the surface of the specimen by scanning a focussed beam of electrons across it.