©2001 timothy g. standish psalm 119:99,100 99 i have more understanding than all my teachers: for...
TRANSCRIPT
©2001 Timothy G. Standish
Psalm 119:99,10099 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.
©2001 Timothy G. Standish
Timothy G. Standish, Ph. D.
Electron Electron MicroscopyMicroscopy
©2001 Timothy G. Standish
History and ApplicationsHistory 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
©2001 Timothy G. Standish
Electron Gun-
A Television MonitorA Television Monitor
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Vacuum
Phosphore coated screen
Magnets
Electron beam
©2001 Timothy G. Standish
Scanning Electron MicroscopyScanning 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
©2001 Timothy G. Standish
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Scanning Electron MicroscopeScanning Electron Microscope
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©2001 Timothy G. Standish
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Scanning Electron MicroscopeScanning Electron Microscope
Magnet “lenses”
Beam deflector
Filament
FocusedElectron beam
Electrons
Stub
Sample
©2001 Timothy G. Standish
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Magnet “lenses”
Beam deflector
Filament
FocusedElectron beam
Electrons
Stub
Sample
Reflected electrons
Electron detector
Scanning Electron MicroscopeScanning Electron Microscope
©2001 Timothy G. Standish
Scanning Electron MicrographsScanning Electron MicrographsMay Fly
Head
Bee Eye
©2001 Timothy G. Standish
More S. E. MicrographsMore S. E. MicrographsLeaf With Bacteria
Anther
Burr
©2001 Timothy G. Standish
Transmission Electron Transmission Electron MicroscopyMicroscopy
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
©2001 Timothy G. Standish
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Transmission Electron MicroscopeTransmission Electron Microscope
Magnet “lenses”
Beam spreader
Filament
FocusedElectron beam
Sample
Electrons
Ultra vacuumTo a very efficient pump
Window
Phosphore coated target
©2001 Timothy G. Standish
Transmission Electron MicrographTransmission Electron MicrographDiaphragm 24,000 XDiaphragm 24,000 X
©2001 Timothy G. Standish
Transmission Electron MicrographTransmission Electron MicrographSperm Tail XS, 28,000 XSperm Tail XS, 28,000 X
©2001 Timothy G. Standish