2.1.3 Methods of studying cells

• Describe the difference between magnification and resolution

  ● Magnification = number of times greater image is than size of the real (actual) object ○ Magnification = size of image / size of real object

  ● Resolution = minimum distance apart 2 objects can be to be distinguished as separate objects
• Principles and limitations of optical microscopes

  • Light focused using glass lenses
  • Light passes through specimen, different structures absorb different amounts & wavelengths
  • Generates a 2D image of a cross-section
  • Low resolution due to long wavelength of light
  • Can’t see internal structure of organelles or ribosomes
  • Specimen = thin
  • Low magnification (x 1500) Can view living organisms
  • Simple preparation
  • Can show colour
• Principles and limitations of transmission electron microscopes

  • Electrons focused using electromagnets
  • Electrons pass through specimen, denser parts absorb more and appear darker
  • Generates a 2D image of a cross-section
  • Very high resolution due to short wavelength of electrons
  • Can see internal structures of organelles and ribosomes
  • Specimen = very thin
  • High magnification (x 1,000,000)
  • Can only view dead / dehydrated specimens as uses a vacuum
  • Complex preparation so artefacts often present
  • Does not show colour
• principles and limitations scanning electron microscopes


  • Electrons focused using electromagnets
  • Electrons deflected / bounce off specimen surface
  • Generates a 3D image of surface
  • High resolution due to short wavelength of electrons
  • Can’t see internal structures
  • Specimen does not need to be thin
  • High magnification (x 1,000,000) Can only view dead / dehydrated
  • specimens as uses a vacuum Complex preparation so
  • artefacts often present
  • Does not show colour