The Electron Microscope

Question 1

When was the electron microscope developed?

Answer 1

1930’s

Question 2

What does the electron microscope use instead of light?

Answer 2

A beam of electrons

Question 3

What are the two main advantages of the electron microscope?

Answer 3

The electron beam has a short wavelength which means it has a higher resolving power.
Electrons are negatively charged so the beam can be focused using electromagnets

Question 4

What happens to electrons in air?

Answer 4

They are absorbed or deflected by the molecules in air

Question 5

What has to be created in an electron microscope in order for it to work correctly?

Answer 5

A near-vacuum

Question 6

Instead of a condenser lense, what does an electron microscope use?

Answer 6

A magnetic condenser

Question 7

What are the two types of electron microscope?

Answer 7

Transmission electron microscope (TEM)

Scanning electron microscope (SEM)

Question 8

Explain how the transmission electron microscope works.

Answer 8

An electron gun produces a beam of electrons that is focused on the specimen by a condenser electromagnet. Parts of the specimen absorb electrons (appear dark) and parts transmit electrons (appear bright). An image is then produced on a screen: photomicrograph

Question 9

What is the resolving power of the TEM?

Answer 9

0.1nm

Question 10

What are the main limitation of using the TEM?

Answer 10

The whole system must be in a vacuum - no living specimens
The specimen must be extremely thin (result is a 2D image)
A complex staining process is required
Artefacts

Question 11

What is good about the SEM?

Answer 11

It can make a 3D image