Microscopy

• Microscopy


  Using microscopes to look at objects too small to be seen by the naked eye
• Light microscope


  • Uses focused light passed through the object and two lenses to magnify an image of the object
• Using a light microscope

  1. Light passes through the object

  2. Light passes through the ×4 objective lens

  3. Light passes through the ×10 eyepiece lens

  4. Image is magnified 40 times
• Magnification


  The degree to which an image is enlarged
• Using a ×10 eyepiece lens and a ×10 objective lens, the image is magnified ×100
• Making a glass slide


  1. Rub a clean cotton bud on the inside of your cheek

  2. Smear the sample across a clean glass slide

  3. Add a few drops of methylene blue dye

  4. Gently lower a glass coverslip onto the sample
• Before undertaking any practical activity, it is important to carry out a risk assessment
• Things to consider in a risk assessment


  • Hazard
  • Risk
  • Control measure
• Methylene blue is an irritant
• If methylene blue comes into contact with skin or eyes


  It could cause irritation
• Control measures


  • Wear laboratory gloves
  • Wear safety glasses
  • Use low concentrations of the chemical
• Glass coverslips are easily broken and are sharp
• Glass coverslips can cut the skin

  When trying to lower onto the slide
• Control measures for glass coverslips


  • Handle carefully
  • Report breakages
• Magnification


  The degree to which an image is enlarged, calculated as image size divided by actual size
• Katie's drawing of onion cells was 40 mm long, the actual cells were 0.4 mm long, so the magnification was ×100
• Calculating magnification


  Magnification = image size / actual size
• Terry's drawing of the same cells was 60 mm long, so the magnification was ×150