Electron Microscopes
- Created by: emilytester
- Created on: 07-04-14 16:53
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- Electron Microscopes
- The Uses of Electrons
- They generate a beam of electrons which have a wavelength 100,000x shorter than light.
- They use magnets instead of lenses to focus the beam of electrons.
- Electrons are not visible to the human eye so the image produced is projected onto a screen to make a black and white image. (greyscale image)
- images are called electron micrographs
- Resolution of the electrons is around 500,000x greater than that or a human eye.
- Transmission Electron Microscopes (TEM)
- The electron beam passes through a very thinly prepared sample
- Electrons pass through the denser parts of the sample more easily which gives the micrograph contrast.
- The final image produced is 2D
- The magnification possible with a TEM is 500,000x
- The electron beam passes through a very thinly prepared sample
- Scanning Electron Microscopes (SEM)
- The electron beam is directed onto a sample and the electrons don't pass through the specimen.
- Electrons are 'bounced off' the sample
- the final image produced is 3D
- The magnification possible with an SEM is 100,000x
- The electron beam is directed onto a sample and the electrons don't pass through the specimen.
- Coloured Electron Micrographs
- Electron micrographs are sometimes shown in colour because colour has been added to show different components.
- 'False-Colour' micrographs.
- All original micrographs are greyscale/ black and white images.
- Electron micrographs are sometimes shown in colour because colour has been added to show different components.
- Disadvantages
- Samples have to be placed in a vacuum
- Electron microscopes are extremely expensive.
- Preparing samples requires a high degree of skills and training.
- The Uses of Electrons
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