3.2.1.5 - Light and Electron Microscopes Flashcards
What you see when looking through a microscope is called the
Image
What are the disadvantages of a light microscope?
- Low resolution due to ‘longer’ wavelength of light.
- Low magnification (X1,250 max)
- Thin specimens may not represent true specimen.
What are the advantages of a light microscope?
- Easy to use (no special training required)
- Cheap (
- True colour images but may sometimes require staining.
- Can observe live specimens
Define microscope resolving power.
The ability of a microscope to differentiate between 2 close together objects.
What is another term for resolution?
Resolving power
What is meant by magnification?
How much bigger an object looks under a microscope.
Magnification = Image Size ÷ Actual Size
What are the advantages of a transmission electron microscope (TEM)?
- High resolving power (0.1 nm)
- High magnification (X500, 000)
- Provides detailed images of internal structures of cells.
Name the 3 main microscopes used by scientists.
- Light microscope
- Scanning electron microscope (SEM)
- Transmission electron microscope (TEM)
What are the advantages of a scanning electron microscope?
- High resolution (20 nm)
- High magnification (X200, 000)
- 3D images
Why do electron microscopes have a greater resolving power than light microscopes?
- They use electrons to interact with the specimen.
- Electrons have a shorter wavelength so interact more witht he specimen.
What are the disadvantages of a transmission election microscope (TEM)?
- Special training is required before use.
- Samples must be dead as electrons are fired through a vacuum and stains containing heavy elements are used.
- ‘Artefacts’ can be present in image from staining process.
- Sample must be 1 cell thick to allow electrons to penetrate specimen.
- Black and white images only so false colour must be used.
- 2D images - 3D possible but complicated and slower than SEM.
- High cost
- High energy electron beams can destroy the specimen.
What is the resolving power of a light microscope and what does this mean?
2 µm
It can differentiate between objects up to that distance apart.
What are the disadvantages of a scanning electron microscope (SEM)?
- Special training is required before use.
- Samples must be dead as electrons are fired through a vacuum and stains containing heavy elements are used.
- ‘Artefacts’ can be present in image from staining process.
- Black and white images only so false colour must be used.
- Cannot see inside specimens.
- High cost
- High energy electron beams can destroy the specimen.
What are the main differences between scanning and transmission electron microscopes?
Does light or electons have the shortest wavelength?
Electrons