microscopy

• Microscopy


  The use of microscopes to study small objects
• Cells are studied using microscopes
• Light microscopes


  • Use light and lenses to form an image of a specimen and magnify it
  • Have developed over the years as technology and knowledge have improved
• Electron microscopes


  • Use electrons instead of light to form an image
  • Have a much higher magnification than light microscopes
  • Have a better resolution (ability to distinguish between points)
• Electron microscopes


  • Let us see much smaller things in more detail, like the internal structures of cells and organelles
  • Even let us see finer things like ribosomes and plasmids
• Magnification


  The ratio of the image size to the real size of the object
• Calculating magnification


  Magnification = image size / real size
• Calculating magnification


  • A specimen is 50 μm wide, calculate the width of the image under 100x magnification
• Standard form


  A way to write very big or small numbers with lots of zeros in a more manageable way, e.g. 0.017 can be written as 1.7 x 10^-2
• A mitochondrion is approximately 0.0025 mm long, written in standard form this is 2.5 x 10^-3 mm
• Preparing a microscope slide

  1. Place a small drop of the specimen on the slide

  2. Carefully lower a cover slip onto the drop to avoid air bubbles
• Using a light microscope

  1. Place the prepared slide on the stage

  2. Start with the lowest power objective lens

  3. Use the coarse adjustment knob to roughly focus the image

  4. Use the fine adjustment knob to get a clear, focused image

  5. Swap to higher power objective lenses to see more detail
• Drawing microscope observations


  1. Draw what you see using a sharp pencil

  2. Make the drawing take up at least half the page

  3. Use clear, unbroken lines with no colouring or shading

  4. Draw subcellular structures in proportion

  5. Include a title and magnification
• You can work out the real size of a cell by counting the number of cells in 1 mm of the image and using the magnification