microscopy

• magnification tells us how many times larger an image is than the real thing
• resolution is the ability to tell the close objects apart
• The first light microscope was made at the end of the 16th century
• light microscopes allow us to see cells and bacteria but not sub cellular structures
• the electron microscope was first used in 1933
• electron microscopes allowed us to see sub cellular structures more clearly
• Practical

  • put a thin sample of onion tissue on a microscope slide
  • add a few drops of iodine
  • place a slide over the tissue and place onto the stage
  • use objective lens to adjust the magnification and focus
  • increase magnification and refocus to see detail
• use the objective lens first so that you can initially focus on the sample
• When using a light microscope, use the lowest power objective lens, and focus on the sample. Increase the power and then refocus.
• When using a light microscope a stain is used to give contrast to the features of the cells, to make them visible.

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