microscopes Flashcards
1
Q
What are the 4 steps to calibrating a microscope?
A
- Place the stage micrometer on the microscope stage.
- Line up the divisions on the eyepiece graticule with those of the micrometer.
- Work out the length of one eyepiece graticule unit in micrometers.
- Repeat for each of the objective lenses on the microscope.
2
Q
Covert into micrometers:
- 2 mm
- 0.5 mm
- 0.01 mm
A
- 2000
- 500
- 10
3
Q
Define magnification.
A
How much bigger the image is than the original object. Usually given as a magnification factor.
4
Q
Define resolution.
What is it measured as?
How would you improve resolution?
A
The smallest separation at which two separate objects can be distinguished.
Measured as a distance.
Use a shorter wavelength of light.
5
Q
LIGHT MICROSCOPES
Advantages?
Limitations?
A
- Relatively cheap, portable so can be used in the field as well as the lab, able to study whole living organisms.
- Low resolving power of 200 nm, very small cell organelles cannot be seen.
6
Q
LASER SCANNING (CONFOCAL)
Advantages?
Limitations?
A
- Images have a high resolution and show high contrast. Able to focus on structures at many different depths. 3D image. Can observe whole organisms and individual cells. Both living n fixed.
- v time consuming as sample is scanned. Lower resolution than electron.
7
Q
TEM
Maximum magnification?
Resolution?
How does it work?
A
-500,000X
-
8
Q
SEM
Maximum magnification?
How does it work?
A
- 100,000X
- 3D
- Electrons are scattered, microscope collects n counts.
9
Q
ELECTRON (sem&tem)
Advantages?
Limitations?
A
- Can produce more detailed images of inside structures. SEM produces 3D not possible with optical. Mag. 2000X better than optical.
- Electron beams are deflected by air molecules so sample must be in vacuum. V V V EXPENSIVE. Requires high level of skill n training. Must be dead. Stains are needed.
10
Q
How do you find the magnification?
A
Image size/ actual size.
