3.2 The Electron Microscope

Question 1

What are the two advantages of an electron microscope?

Answer 1

The electron beam has a very short wavelength, giving a high resolving power.

Electrons are negatively charged, so the beam can be focused using electromagnets.

Question 2

What are the two types of electron microscope?

Answer 2

The transmission electron microscope
&
The scanning electron microscope

Question 3

What are the 3 main limitations of a TEM?

Answer 3

The whole system must be in a vacuum and therefore living specimens cannot be observed.

A complex staining process is required, and the image is only in black and white.

The specimen must be extremely thin.

The image may contain artefacts.

Question 4

What are artefacts?

Answer 4

Things that result from the way the specimen is prepared. They appear on the photomicrograph but are not part of the natural specimen.

Question 5

All the limitations of the TEM also apply to the SEM, except that

Answer 5

the specimens don’t need to be as thin.

Question 6

Which has a high resolving power, SEM or TEM?

Answer 6

TEM

Question 7

What is the difference in images between the SEM and TEM.

Answer 7

SEM is 3-D, TEM is 2-D