BIOS 111 Lecture Notes - Lecture 4: Scanning Electron Microscope, Electron Microscope, Radiography

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8 Feb 2017
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BIOS 111 Lecture 4 (1/18/17)
Structures of prokaryotes can really only be seen with an electron microscope.
They’re visible with light microscopy but you can’t see detail
We needed an extremely high magnification, much stronger than a light microscope, so
the electron microscope was made
If you magnify extremely on a light microscope, it’s blurry. To be able to tell bacteria
apart with visible light microscopy, they need to be separate by about .2µm
The goal is to have high resolution
To what extent can you magnify something and make the information useful?
You can’t see the inside of prokaryotes with light microscopy.
Electrons have a wavelength, so we can substitute them for photons
Electrons can magnify between 100,000X and half a million X
We can see the interior of prokaryotes with electron microscopy
Radio waves are long wavelengths, gamma and X-rays have short wavelengths.
Short wavelengths have lots of energy
Electrons have short wavelengths and high energy, so we can get a much
better resolution
Light can kill microbes or help photosynthetic microbes
Ozone protects humans but we can still get burnt
Electrons are shot down and go through or land on the specimen in electron microscopy
Light microscopes use glass to focus
In electron microscopy, there are magnets to help us focus on the bacteria
With a scanning electron microscope, you are looking only at the outside of the bacteria
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