Microscopy

• Object


  The real object or sample you're looking at
• Image


  The image you see when looking down the microscope
• How light travels in a microscope

  1. Light from the room hits the mirror and is reflected upwards through the object on the stage

  2. It will then pass through one of the objective lenses, through the eyepiece lens, and into our eye

  3. The lenses spread out the light rays so the image we see is far larger than the object
• Magnification


  How many times larger the image is than the object
• Resolution


  • Shortest distance between 2 points on an object, that can still be distinguished as separate
  • A measure of how detailed the image is
  • Lower resolution = more blurry
• Light microscopy


  • Easy to use
  • Relatively cheap
  • Relies on light
  • Resolution limited to 0.2 μm
  • Cannot study subcellular structures
• Electron microscopy


  • Hard to use
  • Very expensive
  • Uses electrons
  • Maximum resolution 0.1 nm
  • 2000 times better than light microscopes
  • Can study subcellular structures
• Atoms: 0.1-0.5 nm (diameter)
• Naked human eye - see to 100 μm
• Light microscope see to 500 nm
• Electron microscope see to 0.1 nm
• Cells 10-100 μm
• Units of conversion - mm

  Micrometres - x1000

  Nanometres - x100,000

  Metres - ÷1000

  Kilometres - ÷100,000
• Magnification = image size ÷ actual size

  Plant cell:

  Real width - 0.02mm

  Image width - 40mm

  Magnification = x2000