Scanning electron microscopes

Question 1

How does a SEM work

Answer 1

SEMs scan a beam of electrons across the specimen

This beam bounces off the surface of the specimen and the electrons are detected, forming an image

This means SEMs can produce three-dimensional images that show the surface of specimens

Question 2

Advantages of SEMs:

Answer 2

They can be used on thick or 3-D specimens

They allow the external, 3-D structure of specimens to be observed

Question 3

SEMs disadvantages

Answer 3

They give lower resolution images (less detail) than TEMs

They cannot be used to observe live specimens (unlike optical microscopes that can be used to observe live specimens)

They do not produce a colour image (unlike optical microscopes that produce a colour image)