Electron microscopes and cell detail

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  • Created by: racheon
  • Created on: 14-04-14 15:16
What is the wavelength of visible light that light microscopes have?
A range from about 400 to 750nm.
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Why can we achieve higher resolutions with electron microscopes than light microscopes?
Because they generate a beam of electrons with a wavelength of 0.004nm.
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What is the minimum distance an electron microscope can distinguish between 2 objects?
0.2nm.
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How do electron microscopes focus the beam of electrons onto a prepared specimen?
By using magnets.
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What part of the electron microscope is not visible to the human eye?
The beam of electrons.
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What happens to the image of the specimen after the electrons have been focused onto it?
It's projected onto a screen or photographic paper to make a black-and-white electron micrograph.
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What are the 2 types of electron microscopes?
The transmission electron microscope and the scanning electron microscope.
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Give 4 key points about the transmission electron microscope.
The electron beam passes through a very thin prepared sample. The electrons pass through the denser parts less easily, giving some contrast. The final image is 2-D. The magnification possible is x500,000.
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Give 3 key points about the scanning electron microscope.
The electron beam doesn't pass through the sample, the electrons are bounced off it. The final image is a 3D view of the surface of the sample. The magnification possible is about x100,000.
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What are the advantages of using electron microscopes?
The resolution is 0.1nmm meaning it can be used to produce detailed images of the structures inside cells. The SEM produces 3D images that can reveal the detail of contours of cellular or tissue arrangements.
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What are the limitations of using electron microscopes?
Electron beams are deflected by molecules in the air, so samples have to be placed in a vacuum. They're expensive. Preparing and using samples requires a high degree of skill and training.
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How do we add colour to electron micrographs, and what do we call coloured images?
Using specialised computer software, and they're called false-colour electron micrographs.
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Define staining.
Any process that helps to reveal or distinguish different features. In electron microscopy, they're metal particles or salts.
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What is the difference between specimens that can be used in light microscopes and specimens that can be used in electron microscopes?
Specimens in light microscopes can be living or non-living, but specimens in electron microscopes have no be non-living.
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Other cards in this set

Card 2

Front

Why can we achieve higher resolutions with electron microscopes than light microscopes?

Back

Because they generate a beam of electrons with a wavelength of 0.004nm.

Card 3

Front

What is the minimum distance an electron microscope can distinguish between 2 objects?

Back

Preview of the front of card 3

Card 4

Front

How do electron microscopes focus the beam of electrons onto a prepared specimen?

Back

Preview of the front of card 4

Card 5

Front

What part of the electron microscope is not visible to the human eye?

Back

Preview of the front of card 5
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