Tpyes of Microscope

• Light Microscope: A type of microcope which has a condenser, objective lens and eyepiece lens and light is passed through the thin specimen and up through the objective and eyepiece lenses to the eye.
• Labelling a Microscope:

  A) Coarse focus knob

  B) fine focus knob

  C) light/mirror

  D) stage

  E) objective lens

  F) eyepiece lens

  
• Electron Microscope: Beams of electrons are used to visualise strucutures in a vaccum. Electrons have a smaller wavelength than light so electron microscopes have a higher resolution.
• Scanning Electron Microscope: A type of microscope whuch bounces beams of electrons off the surface of an object to develop a 3D image of the specimen (no need for thin sections).
• Transmission Electron Microscope: A type of microscope which asses a beam of electrons through a very thin section of specimen (which often has to be stained with heavy metals to show up fine internal strcutures.
• Light microscopes have a poor resolution as a result of a relatively long wavelength.
• The electron microscope was developed in the 1930s.
• The electron beam has a very short wavelength and the microscope can therefore resolve objects well - it has a high resolving power.
• As electrons are negatively charged, the beam in an electron microscope can be focused using electromagnets.
• The two types of electron microscope:

  • Scanning electron microscope
  • Transmission electron microscope
• The light microscope has uses light are radiation.
• Electron microscopes use electrons are a radiation source.
• Light microscopes use condenser lenses, whilst electron microscopes use magnetic condensers.
• The maximum magnification for a light microscope is x1500
• The maximum magnification for an SEM is x250000
• The maximum magnification for a TEM is x500000
• The maximum resolution for a light microscope is 200nm.
• The maximum resolution for a TEM is 20nm.
• The maximum resolution for a SEM ia 0.2nm,
• In a light microscope, specimens jave to be thin, but they can be alive.
• In a TEM, specimens have to be dead and extremely tin.
• In a SEM speciments have to be dead but they don't have to be thin.
• In a light microscope, the cells are stained, usually with iodine.
• In a SEM, cells don't need to be stained.
• In a TEM, cells need to be stained using heavy metals.