2.1.4 Magnification and Resolution

• What is the formula for magnification?

  magnification = size of image ÷ size of real object
• What can the magnification formula be rearranged to calculate?

  magnification, size of image, size of real object
• What does the magnification equation triangle represent?

  • I = Image/Drawing Size
  • A = Actual Size of Image
  • M = Magnification
• What unit is typically used to measure the actual size of cells?

  micrometre (µm)
• What unit is sometimes used to measure internal cellular structures?

  nanometres (nm)
• What units are usually used to measure the size of images?

  centimetres (cm) or millimetres (mm)
• How do the units of measurement relate to each other?

  • 1000 nm = 1 µm
  • 1000 µm = 1 mm
  • 1000 mm = 1 m
  • 10 mm = 1 cm
• Why is it essential to have the same units during magnification calculations?

  To ensure accurate calculations
• How do you convert larger units to smaller units?

  Multiply by the relevant factor
• How do you convert smaller units to larger units?

  Divide by the relevant factor
• Does magnification have units?

  No, magnification does not have units
• What is the actual size of a cell if the image size is 30 mm and magnified by ×3000?

  • A = I ÷ M
  • A = 30 mm ÷ 3000 = 0.01 mm
  • 0.01 mm = 10 µm
• What is the actual thickness of the leaf in the example?

  2000 µm
• What is the image size of the leaf in the diagram?

  50 mm
• How do you calculate the magnification of the diagram?

  magnification = image size ÷ actual size
• What is the magnification if the image size is 50,000 µm and actual size is 2000 µm?

  25
• How is magnification defined?

  • The number of times larger an image is than the actual object
• What factors affect the ability of a microscope to magnify an object?

  • Type of microscope
  • Features of the microscope
• How is resolution defined?

  • Ability to distinguish separate points as two objects
• What does higher resolution allow in microscopy?

  To distinguish objects at shorter distances
• What limits the resolution of light microscopes?

  The wavelength of light
• What happens to light as it passes close to physical structures?

  It is diffracted, spreading out
• What is the resolving power of electron microscopes compared to light microscopes?

  Much higher due to smaller wavelength
• What are the maximum resolutions of light and electron microscopes?

  • Light microscopes: 200 nm
  • Electron microscopes: 0.5 nm (TEM) or 3-10 nm (SEM)
• What are the maximum magnifications of light and electron microscopes?

  • Light microscopes: ×1500-2000
  • Electron microscopes: more than ×500,000
• What are the differences in specimen usage between light and electron microscopes?

  • Light microscopes: living or dead specimens
  • Electron microscopes: only dead specimens
• What are the advantages of light microscopes?

  • Small and easy to carry
  • No vacuum needed
  • Easy sample preparation
• What are the disadvantages of electron microscopes?

  • Large and immobile
  • Requires vacuum
  • Complicated sample preparation
• What should students appreciate about the values of resolution and magnification in different microscopes?

  How the values differ between types