Microscopy Flashcards
1
Q
Define resolution
A
Minimum distance between 2 points where they can be seen apart.
2
Q
Define magnification
A
The number of times the bigger the image appears compared to the actual size.
3
Q
What are the advantages of electron microscopy?
A
- Uses electrons that have a shorter wavelength than light & great resolution
- Higher magnification in light microscopes blur images, electron has higher resolution
4
Q
What are the disadvantages of electron microscopy?
A
- A vacuum is required, living specimens can’t be seen
- Preparation & staining are more complicated than light microscopes, artefacts could be produced.
- Expensive and training is required
5
Q
What is TEM?
A
- Transmission electron microscope.
- Beam of electrons transmitted through specimen which is thin and stained using electron dense substances, e.g heavy metal salts.
- Substances deflect electron beam and remaining electrons produce an image when passing through specimen.
6
Q
Why is TEM good/bad?
A
\+Higher resolution than SEM. \+Can see internal structures -Very thin sections required -Doesn't show 3D arrangement -Specimen gradually deteriorates in electron beam.
7
Q
What is SEM?
A
- Specimen is coated with a thin film of a heavy metal, e.g. gold
- Electron beam scans to and fro across specimen
- Electrons reflected from the surface are collected & produce an image on screen.
8
Q
Why is SEM good/bad?
A
+Surface structures are shown
+Gives 3D effect.
-Lower resolution than TEM
-Only the surface of an object can be viewed.
9
Q
What is the calculation for microscopy?
A
Image size (I)/ Magnification (M) X Actual size (A)
10
Q
What is the conversion for mm, um and nm?
A
Mm –> X 1000 –> um –> X 1000 –> nm
/
Mm
