Mic4oscopes

• Light microscopes can be used to observe things that are too small to see with the naked eye
• Cells are too small to see with the naked eye
• To find out about their structure, they can be viewed under a light microscope
• The Compound Light Microscope

  • Eyepiece
  • Nosepiece
  • Objective lenses
  • Stage
  • Rough focus
  • Fine focus
  • Clip
  • Lamp
• To prepare a slide of onion cells

  1. Peel off a layer of onion and remove its inner skin using forceps

  2. Place the thin layer flat onto a glass slide

  3. Add a drop of iodine solution on top of the sample

  4. Carefully lower a cover slip over the sample using the forceps
• To prepare a slide of cheek cells

  1. Add a drop of iodine solution to an empty glass slide

  2. Using the blunt end of the toothpick, gently scrape the inside of your cheek

  3. Swirl the end of the toothpick in the drop of iodine

  4. Carefully lower a cover slip over the sample using the forceps
• Observing the cells

  1. Place the slide on the microscope stage

  2. Use the coarse adjustment knob to move the stage up and down

  3. Position the lowest magnification lens (usually x40) as close to the slide as possible, without touching it

  4. Look through the eyepiece and slowly turn the coarse adjustment knob to move the stage away from the lens

  5. Use the fine adjustment knob to bring the image into focus

  6. Swap to a lens with a higher magnification and use the fine adjustment knob to bring the cells back into focus

  7. Sketch and label a diagram of the cells you can see
• Magnification

  How many times bigger the image of the cell is than the object
• Calculating magnification

  1. Total magnification = eyepiece lens magnification x objective lens magnification

  2. Magnification = image size / real size
• Scientific drawings should never be coloured in or use shading
• This is picture of microscope

  
• Iodine makes cell easier to see
• A coverslip is placed over the stained onion cells. This prevents the specimen and stain getting on the objective lens.
• How to make test fairer

  Start with potato chips of the same mass
• Light source ➔ stage ➔ microscope slide ➔ object ➔ objective lens ➔ body tube ➔ eyepiece lens ➔ eye
• Conversion

  nm(÷1000)->um(÷1000)->mm(÷1000)->m(÷1000)km