Microscopy

• What is microscopy?

  Use of microscopes to view small objects
• Why do scientists use microscopes?

  To study cells, tissues, and microorganisms
• What does a light microscope use to magnify images?

  Visible light and glass lenses
• What is the maximum magnification of a light microscope?

  Around ×1500
• What is the maximum resolution of a light microscope?

  200 nm (nanometers)
• What are the advantages of using a light microscope?

  • Can view living cells
  • Relatively cheap and easy to use
  • Can observe specimens in color
• What are the disadvantages of using a light microscope?

  • Limited magnification and resolution
  • Cannot see detailed structures inside cells
• What does an electron microscope use to create an image?

  Beams of electrons
• What are the two types of electron microscopes?

  1. Transmission Electron Microscope (TEM)
  2. Scanning Electron Microscope (SEM)
• What does a Transmission Electron Microscope (TEM) do?

  Electrons pass through the specimen
• What is the maximum magnification of a TEM?

  Up to 2,000,000×
• What is the resolution of a TEM?

  ~0.2 nm
• What does a Scanning Electron Microscope (SEM) do?

  Electrons bounce off the specimen’s surface
• What is the maximum magnification of a SEM?

  Around 200,000×
• What is the resolution of a SEM?

  ~10 nm
• What are the advantages of electron microscopes?

  • Higher magnification and resolution than light microscopes
  • Can see sub-cellular structures in detail
• What are the disadvantages of electron microscopes?

  • Very expensive
  • Large and not portable
  • Requires a vacuum (specimens must be dead)
  • Only black-and-white images (false color possible)
• What is magnification in microscopy?

  How much larger the image appears
• What is resolution in microscopy?

  The ability to distinguish between close objects
• What is field of view in microscopy?

  The visible area seen through a microscope
• What is staining in microscopy?

  Using dyes to make specimens more visible
• What is the formula for magnification?

  Image size / Actual size
• If a cell appears 50 mm with a magnification of ×500, what is its actual size?

  $0.1 \text{ mm}$
• What are the units of measurement in microscopy?

  • Millimeter (mm): 1 mm = 1000 μm
  • Micrometer (μm): 1 μm = 1000 nm
  • Nanometer (nm): 1 nm = 0.001 μm
• What are the practical steps for using a light microscope?

  1. Prepare the slide with a thin specimen
  2. Add a drop of stain and place a coverslip
  3. Start with low magnification, then increase
  4. Focus using coarse and fine focus
  5. Measure using a graticule
• What is the aim of the required practical using a microscope?

  • To observe, draw, and measure cells
• What are the results expected from the practical investigation of cells?

  • A labeled drawing of observed cells
  • Calculated actual size using magnification formula
• What are the differences between light and electron microscopes?

  • Light: Up to ×1500 magnification, ~200 nm resolution, color images
  • Electron: Up to ×2,000,000 magnification, ~0.2 nm resolution, black & white images
• How has microscopy advanced biology?

  • Development of cell theory
  • Discovery of organelles
  • Medical advancements in treatments and vaccines