Microscopes

• Microscopes and magnification


  As microscope technology has developed over time, we have been able to see more of the structures of cells and to know more about the role of sub-cellular structures
• Using microscopes


  1. Before microscopes were invented about 350 years ago, people could not see the cells in organisms

  2. Magnification enables you to see plant cells, animal cells and bacterial cells, and the structures inside them
• Light microscope


  • Uses light to magnify objects
  • The greatest possible magnification using a light microscope is about x2000
• Electron microscope


  • Uses electrons to view an object
  • Makes it possible to magnify objects up to about x10 million
  • You can see objects in cells more clearly and in far more detail with an electron microscope than with a light microscope
• • Measure image in millimetres (mm)
  • Multiply by 1000 to get measurement in micrometres (um)
  • If the image has a scale bar, use that to find the answer
• Calculating magnification


  Magnification (M) = image size (I) / real size (R)
• Using a light microscope safely

  1. Always start with the lowest power objective under the eyepiece

  2. Clip the slide securely on the stage

  3. Adjust the light source (mirror) so that light goes up through the slide

  4. Use the coarse focusing wheel to focus on the slide

  5. Move the slide so that the cell you will draw is in the middle of the view

  6. If needed, move a higher power objective into position above the slide

  7. Use the fine focusing wheel to bring the cell back into focus
• • If you use the highest power objective, you could damage the slide or eyesight
  • Never look directly at the light source when focusing, as this could damage your eyes