Microscopy

• Microscopy


  The study of objects using microscopes
• Microscopes are important for biology
• Microscopes


  • Let us see things we can't see with the naked eye
  • Microscopy techniques have developed over the years as technology and knowledge have improved
• Light microscopes


  Use light and lenses to form an image of a specimen and magnify it
• Electron microscopes


  • Use electrons instead of light to form an image
  • Have a much higher magnification and resolution than light microscopes
• Electron microscopes


  • Let us see much smaller things in more detail, like the internal structure of mitochondria and chloroplasts, and even tinier things like ribosomes and plasmids
• Calculating magnification


  Magnification = image size / real size
• Preparing a slide for a light microscope


  1. Add a drop of water to the middle of a clean slide

  2. Cut up an onion and separate it out into layers. Use tweezers to peel off some epidermal tissue from the bottom of one of the layers

  3. Place the epidermal tissue into the water on the slide

  4. Add a drop of iodine solution

  5. Place a cover slip on top
• Parts of a light microscope

  • Eyepiece
  • Coarse adjustment knob
  • Fine adjustment knob
  • High and low power objective lenses
  • Light
  • Stage
• Using a light microscope


  1. Clip the slide onto the stage

  2. Select the lowest-powered objective lens

  3. Use the coarse adjustment knob to move the stage up to just below the objective lens

  4. Look down the eyepiece and use the coarse adjustment knob to move the stage downwards until the image is roughly in focus

  5. Adjust the focus with the fine adjustment knob, until you get a clear image

  6. If you need greater magnification, swap to a higher-powered objective lens and refocus
• Drawing observations from a microscope


  • Draw with a sharp pencil
  • Drawing should take up at least half the space and have clear, unbroken lines
  • No colouring or shading
  • Subcellular structures should be drawn in proportion
  • Include a title and magnification
  • Label important features with straight, uncrossed lines
• You can work out the real size of a cell by counting the number of cells in 1 mm of the sample
• Magnification of drawing


  Magnification = length of drawing of cell / real length of cell