1. ©2001 Timothy G. Standish Psalm 119:99,100 99 I have more understanding than all my teachers: for thy testimonies are my meditation. 100 I understand more than the ancients, because I keep thy precepts.

2. ©2001 Timothy G. Standish Timothy G. Standish, Ph. D. Electron Microscopy

3. ©2001 Timothy G. Standish History and Applications Electron microscopes were developed around the same time as the development of television sets and utilize much of the same technology They take advantage of the short wavelength of electrons. As the wavelength is shorter, higher resolution is possible than with regular light microscopes Scanning Electron Microscopes (SEM) are analogous to dissecting microscopes Transmission Electron Microscopes (TEM) are similar in principle to compound microscopes

4. ©2001 Timothy G. Standish Electron Gun - A Television Monitor + Vacuum Phosphore coated screen Magnets Electron beam

5. ©2001 Timothy G. Standish Scanning Electron Microscopy SEM is very good for looking at surfaces SEM gives almost infinite depth of field SEM cannot show color With the right detectors SEM can be used to determine the elements in a sample SEM can go to high magnifications, but cannot achieve magnifications as high as those achieved with Transmission Electron Microscopy

6. ©2001 Timothy G. Standish …..….. Scanning Electron Microscope - +

7. ©2001 Timothy G. Standish + - Scanning Electron Microscope Magnet “lenses” Beam deflector Filament Focused Electron beam Electrons Stub Sample

8. ©2001 Timothy G. Standish …..….. - + Magnet “lenses” Beam deflector Filament Focused Electron beam Electrons Stub Sample Reflected electrons Electron detector Scanning Electron Microscope

9. ©2001 Timothy G. Standish Scanning Electron Micrographs May Fly Head Bee Eye

10. ©2001 Timothy G. Standish More S. E. Micrographs Leaf With Bacteria Anther Burr

11. ©2001 Timothy G. Standish Transmission Electron Microscopy TEM allows for very high magnification due to the short wavelength of electrons TEM is very good for looking inside cells, but is not very good for studying surfaces Preparation of samples for TEM is time consuming and difficult No natural color is possible with transmission electron micrographs

12. ©2001 Timothy G. Standish + - Transmission Electron Microscope Magnet “lenses” Beam spreader Filament Focused Electron beam Sample Electrons Ultra vacuum To a very efficient pump Window Phosphore coated target

13. ©2001 Timothy G. Standish Transmission Electron Micrograph Diaphragm 24,000 X

14. ©2001 Timothy G. Standish Transmission Electron Micrograph Sperm Tail XS, 28,000 X

15. ©2001 Timothy G. Standish