4.1.1.5 microscopy

• When were the first light microscopes discovered?

  In mid-17th century
• how do light microscopes work?

  they use a beam of light to form an image of an object
• when was the electron microscope invented?

  1930s
• what did the invention of the electron microscope allow scientists to do?

  understand more about sub-cellular structures inside cells
• how do electron microscopes work?

  they use a beam of electrons to form an image
• what kind of image does a transmission electron microscope give?

  a 2D image with a high magnification and resolution
• what kind of image does a scanning electron microscope give?

  a 3D image but lower magnification
• what is the main difference between light and electron microscopes?

  the resolution and magnification
• what are the benefits to light microscopes?

  they are:

  • Small and profitable
  • Images viewed in colour
  • Can view live specimens
  • Cheaper
  • Easier to use
• what are the limitations to light microscopes?

  they have:

  • Lower magnification than electron microscopes
  • Lower resolution than electron microscopes
• what are the benefits to electron microscopes?

  they have:

  • Higher magnification than a light microscope
  • Higher resolution than a light microscope
• what are the limitations to electron microscopes?

  they are:

  • Large and not portable
  • need specialist training
  • Can’t view live specimens
  • Images only in black and white
  • Expensive
• what is the formula for magnification?

  magnification = $\frac{size\ of\ image}{size\ of\ real\ object}$