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Microscopy & Resolution
Magnification: Image size/Object sizeResolution: The fineness of detail that can be
distinguished in an image.
Highest Typical ResolutionOptical Microscope ~200 nmElectron Microscope ~0.1 nm
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Definitions
Acceptance angle
Numerical ApertureNA = nsin
Rayleigh resolution criterion for a circularaperturex= 0.61 /NA
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OPTICAL MICROSCOPES
Image construction for a simple biconvex lens
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Rayleigh criterion for resolution
www.microscopy.fsu.edu ; www.imb-jena.de
See more interactive tutorials at www.microscopy.fsu.edu
Numerical Aperature Resolution Rayleigh Criterion
http://www.microscopy.fsu.edu/primer/anatomy/anatomyjava.htmlhttp://www.microscopy.fsu.edu/primer/java/nuaperture/index.htmlhttp://www.microscopy.fsu.edu/primer/java/imageformation/airyna/index.htmlhttp://www.microscopy.fsu.edu/primer/java/imageformation/rayleighdisks/index.htmlhttp://www.microscopy.fsu.edu/primer/java/imageformation/rayleighdisks/index.htmlhttp://www.microscopy.fsu.edu/primer/java/imageformation/airyna/index.htmlhttp://www.microscopy.fsu.edu/primer/java/nuaperture/index.htmlhttp://www.microscopy.fsu.edu/primer/anatomy/anatomyjava.html8/2/2019 Microscopy & Resolution
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ComparisonBright-Field
Dark-
Field Fullapertureisilluminated
A centralobstruction blocksthe central cone.
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Dark-Field
Optical Microscopy
A central obstructionblocks the central cone.
The sample is onlyilluminated by the
marginal rays.
These marginal rays mustbe at angles too large forthe objective lens tocollect.
Only light scattered by theobject is collected by the
lens.
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Dark-Field
Optical
Microscopy
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THE ELECTRON MICROSCOPE
The wavelength of the electron can be tuned by changing the
accelerating voltage.
de Broglie : = h/mv: wavelength associated with the particleh: Planks constant 6.6310-34 Js;
mv: momentum of the particleme= 9.110
-31 kg; e= 1.610-19 coulomb
P.E eV = mv2 = h/(2meV) = 12.3/V (for Vin KV, in )Vof 60 kV, = 0.05 x~ 2.5 Microscopes using electrons as illuminating radiation
TEM & SEM
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Components of the TEM
1. Electron Gun: Filament, Anode/Cathode
2. Condenser lens system and its apertures
3. Specimen chamber
4. Objective lens and apertures
5. Projective lens system and apertures
6. Correctional facilities (Chromatic, Spherical, Astigmatism)
7. Desk consol with CRTs and camera
Transformers: 20-100 kV; Vacuum pumps: 10-6 10-10 Torr
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Schematic of E Gun & EM lens
Magnification: 10,000 100,000; Resolution: 1 - 0.2 nm
www.udel.edu
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TEM IMAGES
www.udel.edu ; www.nano-lab. com ; www.thermo.com
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