1. Topic 1
Microscopes

2. Light Microscopes How do they work? Benefits Limitations
Pass light through thin specimen.
Benefits
Limitations
Benefits: See true colors. Specimen can be alive. Observe physiological processes.
Limitations: Magnification and resolution not as high as some other microscope types.

3. Light Microscope Compound Light Microscope Optical lens Objective lens
10x
Objective lens
4x  scanning power
40x
100x  Oil immersion
Total magnification = optical x objective mag.

4. Measuring length? Look at the field of view Using a clear ruler…
OBJ 3
Measuring length?
Look at the field of view
Using a clear ruler…
3.5 mm

5. OBJ 3
Measuring length?
Estimate
How big is each cell?

6. Magnification – Increase in Apparent Size
Increased magnification  Decreased field of view

7. Resolution – A Measure of Clarity
Limited by light wavelength for a light microscope.

8. Magnification vs. Resolution
Magnification - increase in apparent size
Resolution - measure of clarity
Ability to show two objects as separate
Human eye has limit of 0.1 mm
Light microscope has limit of 0.2 micrometer (at any magnification)
Limited by light wavelength.
Longer wavelengths = lower resolution
Limited by light wavelength for a light microscope.

9. Fluorescence Confocal Microscopy
Type of light microscopy: Fluorescence is used to increase resolution.
Specific molecules are tagged with fluorescent dyes
Allows you to see the specific structures of the cell
Here: cytoskeletal filaments, nucleus, etc.
A type of light microscopy. Fluorescing structures are easier to see. Fluorescence increases resolution.

10. Fluorescence Confocal Microscopy
Type of light microscopy.

11. Electron Microscopes Use a beam of electrons instead of light Benefits
OBJ 2
Electron Microscopes
Use a beam of electrons instead of light
Benefits
Resolution = 2nm
Magnification above 50 million x
Limitations
SEM and TEM

13. Transmission Electron Microscope (TEM)
OBJ 2
Transmission Electron Microscope (TEM)
Spinach Cell Chloroplast

14. OBJ 2
TEM
Mitochondrion 14

15. OBJ 2
TEM
Red Blood Cell in a capillary of the pancreas

16. Scanning Electron Micrscope (SEM)
OBJ 2
Scanning Electron Micrscope (SEM)

17. OBJ 2
SEM
Fish gills

18. OBJ 2
SEM
Spider foot

19. OBJ 2
SEM

20. OBJ 2
SEM
tapeworm

21. Comparing microscopes
Light
SEM
TEM
Source
Light Beam
Electron Beam
Resolution limit
2 micrometer
(smallest bacteria)
2 nanometer
(0.002 micrometer)
Properties of Specimen
Thin
Small enough to fit in chamber of scope
Ultra Thin
Other
Can be alive, allows you to see processes and movement
Coated in metal atoms and put in a vacuum (dead)