SEM

Question 0

SEMs use I. Identifying counterfeit drugs…..

Answer 0

Drugs have nano codes on each pill, this stores a range of info about manufacture place and batch number etc.

Code can only be detected by SEM - SEM is mostly unavailable to counterfeiters

Question 1

4 advantages over light microscopy…..

Answer 1

Non destructive
No need for thin sections
Magnify greater than light microscope
Controlled by computer software

Question 2

Electron beam is ……. Across sample surface from one side to the other

Answer 2

Scanned / rastered

Question 3

When one line is scanned, beam moves back and……

Answer 3

Scans a line underneath…. Process is repeated for entire sample

Question 4

Sample prep advantages…..

Answer 4

Not much prep required, therefore small extraterrestrial samples can be analysed

Question 5

Sample size should be only a few cm squared be so that….

Answer 5

It can fit in the sample chamber

Question 6

The sample must be a …. And must be dry

Answer 6

A solid

Question 7

Sample must be held securely on the stage as it……

Answer 7

Allows movement in all directions

Question 8

Thin sections can be mounted on….. Solid samples can be mounted on……

Answer 8

Plates

Stubs

Question 9

Electrically insulating samples (rocks) are usually covered with a conducting material, such as carbon or graphite, because…..

Answer 9

Secondary electrons have low energies and are therefore prone to deflection by any charge on sample surface.
This results in a build up of electrical charge and any image will appear to drift across the screen.

Question 10

A positive electrode is used to…..

Answer 10

Accelerate and focus electrons towards the sample surface

Question 11

Interactions between electron beam and sample occur at the top of the beam, resulting in several emissions…… (5)

Answer 11

Back scattered electrons
Secondary electrons
X rays 
Light
Heat