Microscopes- Practical

• Light microscope

  • Microscope slide
  • Cover slip
  • Onion
  • Forceps
  • Iodine solution
  • White tile
  • Scalpel
  • Any other prepared plant and animal cell slides
• Microscopy

  1. Peel off an epidermal layer on the onion using forceps

  2. Mount onto the microscope slide with a drop of water using a pipette, making sure the tissue lies flat

  3. Add 2 drops of iodine solution to stain the cells

  4. Place the cover slip on by first placing one edge down on the slide and slowly lowering the other side of the cover slip using forceps. Make sure no air bubbles are trapped

  5. Remove any excess stain by soaking it with paper towels

  6. Place the slide on the stage of the microscope

  7. Turn the nosepiece to select a low power objective

  8. Set up the microscope - don't look into the eyepiece yet. Instead, use the coarse adjustment knob to raise the stage until the cover slip just touches the objective

  9. Now look into the eyepiece and turn the coarse adjustment knob to move the stage away until the image comes into focus (doing this helps avoid you breaking the slide)

  10. Turn the nosepiece to select a high power objective

  11. Repeat the same process as above and then look into the eyepiece and turn the fine adjustment knob until the image comes into focus

  12. Make a labelled drawing of a few of the cells you can see, including any features eg. cell wall, nucleus. Write down the magnification

  13. Repeat these steps using a prepared slide
• Optical microscope


  Used to look at cells on a prepared microscope slide
• Optical microscope


  • Has a stage to place the microscope slide
  • Has a light source (lamp or mirror) to illuminate the slide
  • Has objective lenses with different magnifications (4x, 10x, 40x)
  • Has an eyepiece lens with 10x magnification
  • Has coarse and fine focusing dials
• Using an optical microscope to view a prepared slide


  1. Place slide on stage and secure with clips

  2. Select lowest power (4x) objective lens

  3. Slowly turn coarse focus dial to lower lens until it almost touches slide

  4. Look through eyepiece and turn coarse focus dial to bring cells into focus

  5. Use fine focus dial to sharpen focus

  6. Calculate total magnification by multiplying eyepiece (10x) and objective (4x, 10x, 40x) lens magnifications
• What you might see under an optical microscope

  • Animal cells: nucleus, cytoplasm, cell membrane, possible mitochondria
  • Plant cells: cell wall, cytoplasm, nucleus, possible vacuole and chloroplasts
• An optical microscope can only show limited detail compared to other microscopes
• Drawing a magnification scale is important when making drawings from an optical microscope