Electron Microscopy

• What type of microscope do scientists use to see structures smaller than 0.2 µm?

  Electron microscopes
• How is the resolution of a microscope defined?

  Smallest distance between two visible points
• What do electron microscopes use to produce an image?

  Electrons instead of light
• When were electron microscopes developed?

  In the 1930s
• Why were electron microscopes developed?

  To see in greater detail than before
• How is greater resolution achieved in electron microscopes?

  By using high-energy electrons as light source
• What is the smallest distance that can be seen with a light microscope?

  $0.2 \mu m$ (or $2 \times 10^{-7} m$)
• What are the key differences between light microscopes and electron microscopes?

  • Light microscopes use light; electron microscopes use electrons.
  • Light microscopes have a resolution limit of $0.2 \mu m$; electron microscopes can see smaller structures.
  • Electron microscopes provide greater detail than light microscopes.
• Label all parts of an Electron Microscope.

  A) source

  B) beam

  C) electromagnetic

  D) viewing screen

  E) specimen

  
• What is a key advantage of light microscopes?

  Cheap to buy and operate
• What is a key disadvantage of light microscopes?

  Resolution up to 0.2 µm
• Why are light microscopes considered portable?

  They are small and easy to move
• What type of images do light microscopes produce?

  Natural colour of the sample
• Can light microscopes observe living specimens?

  Yes, they can observe living specimens
• What is the resolution limit of light microscopes?

  0.2 µm
• What is a key advantage of electron microscopes?

  Higher resolution up to 0.1 nm
• Why are electron microscopes considered difficult to move?

  They are large and heavy
• What type of images do electron microscopes produce?

  Black and white images
• Can electron microscopes observe living specimens?

  No, specimens are dead
• What is the resolution limit of electron microscopes?

  0.1 nm
• What are the advantages and disadvantages of light and electron microscopes?

  Light Microscope:

  • Advantages:
  • Cheap to buy and operate
  • Small and portable
  • Simple sample preparation
  • Natural colour seen
  • Can observe living or dead specimens
  • Resolution up to 0.2 µm

  
  

  • Disadvantages:
  • Limited resolution

  
  

  Electron Microscope:

  • Advantages:
  • High resolution up to 0.1 nm

  
  

  • Disadvantages:
  • Expensive to buy and operate
  • Large and difficult to move
  • Complex sample preparation
  • Black and white images only
  • Can only observe dead specimens
• What are the two types of electron microscopes?

  Transmission and scanning electron microscopes
• How do transmission electron microscopes (TEM) produce images?

  A beam of electrons passes through a thin slice
• What is the main function of a transmission electron microscope?

  To produce the most magnified images
• How does a scanning electron microscope (SEM) create an image?

  It sends a beam of electrons across a surface
• What is the difference in the type of images produced by TEM and SEM?

  TEM produces magnified images, SEM produces 3D images
• What are the key features of transmission electron microscopes (TEM)?

  • Produce the most magnified images
  • Work like light microscopes
  • Use a beam of electrons through thin samples
  • Focused beam creates an image
• What are the key features of scanning electron microscopes (SEM)?

  • Produce three-dimensional images
  • Send a beam of electrons across surfaces
  • Collect reflected electrons to form images
• What has allowed scientists to see detail within subcellular structures?

  The development of electron microscopy
• What type of structures can be observed in detail using electron microscopy?

  Subcellular structures, such as chloroplasts
• How does electron microscopy enhance our understanding of cellular structures?

  It reveals details within subcellular structures