3.2 - The Electron Microscope

Question 1

Why do light microscopes have a poor resolution?

Answer 1

As a result of the relatively long wavelength of light

Question 2

What are the two main advantages of the electron microscope?

Answer 2

• the electron beam has a very short wavelength and the microscope can therefore resolve objects well - it has a high resolving power
• as electrons are neg charged the beam can be focused using electromagnets

Question 3

What is one condition that needs to happen for the electron microscope to work?

Answer 3

Because electrons are absorbed or deflected by the molecules in air, a near vacuum has to be created within the chamber of the electron microscope

Question 4

What are the two types of electron microscope?

Answer 4

• the transmission electron microscope (TEM)
• the scanning electron microscope (SEM)

Question 5

What are the 4 limitations of the TEM?

Answer 5

• the whole system must be in a vacuum and therefore living specimens cannot be observed
• a complex ‘staining’ process is required and even then the image is not in colour
• the specimen must be extremely thin
• the image may contain artefacts

Question 6

Is the TEM image produced 2D or 3D?

Answer 6

2D

Question 7

All the limitations of the TEM apply to the SEM except one, which one?

Answer 7

The specimens don’t need to be extremely thin

Question 8

Out of the TEM and the SEM, which has the highest resolving power?

Answer 8

TEM