microscopy

• light microscopes use light and lenses to form an image and magnify it, they show individual cells and large subcellualar structures (e.g nuclei)

  electron microscopes use electrons to form an image (so have a higher resolution and a higher magnification than light microscopes) they show much smaller things (e.g plasmids or the internal structures of mitrocondria)
• the formula for magnification:

  magnification = image size / actual size
• microscopy practical (preparing the slide):

  1. put a drop of water in the middle
  2. use tweezers to peel off epidermal tissue from an onion layer
  3. put it into the water
  4. add a drop of iodine solution (a stain)
  5. place a cover slip on top
• microscopy practical (using a light microscope):

  1. clip the slide onto the stage
  2. use the lowest-powered objective lense
  3. use the coarse adjustment knob to move the stage closer to the objective lense
  4. use the eyepiece and the coarse adjustment knob to move the stage untill its roughly in focus
  5. get a clear focus using the fine adjustment knob
  6. for greater magnification swap to a higher-powered objective lense