Microscopes Flashcards
3.2.1.3
1
Q
Define magnification
A
Magnification is how much bigger a sample appears to be under the microscope than it is in real life
2
Q
Define resolution
A
The minimum distance apart that 2 objects can be in order for them to appear as separate items (the absolute to distinguish between two points on an image)
3
Q
Describe a light microscope
A
- uses a beam of light focused by a glass lenses
- light has a longer wavelength than electrons so light microscope has lower resolution than electron microscopes
- light penetrates sample
- specimen needs to be thin (1 cell)
- 2D image
- Image seen in colour due to stain
- living specimen can be viewed
4
Q
Describe a TEM microscope.
A
- uses a beam of electrons focused by electromagnets
- elections have a shorter wavelength than light so TEM has higher resolution than light microscope
- electrons penetrate sample
- specimen needs to be extremely thin
- 2D image
- Image seen in black and white
- in a vacuum so can’t view live specimen
5
Q
Describe a SEM microscope
A
- uses a beam of electrons focused by electromagnets
- electrons have shorter wavelength than light so SEM has higher resolution than light microscope
- electrons bounce off the surface of the sample
- 3D image
- image seen in black and white
- in a vacuum so no live specimens
6
Q
How do you prepare a slide for a microscope? (Light microscope)
A
- thin, often 1 cell thick so light can pass through
- stained so you can distinguish between different components
- sample is placed on slide with a drop of water so the sample doesn’t dry out
- cover slip on top, lowered with a mounted needle to prevent bubbles