Microscopes

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  • Created by: Abby
  • Created on: 24-09-12 20:16
Key Words: Resolution & Magnification
Resolution: the degree to which it is possible to distinguish between two objects that are very close together (higher resolution=greater detail) Magnification: The degree to which the size of an image is larger than the object itself.
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What Are the Different Type of Microscopes?
There are 2 Main: Light and Electron, However Electron Microscopes have 2 different types: Transmission Electron Microscope (TEM) and Scanning Electron Microscope
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What are the Differences between TEM AND SEM?
TEM- Electron beam passed through thin prepared sample; the electrons pass through denser parts less easily, Image is 2D, magnification= x500,000 SEM: Electron Beam directed on sample- bounces off, 3D view of surface. Magnification = x 100,000
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Advantages of Light Microscopes
Cheap to buy, Cheap to run, Living and Dead Tissue can be observed.
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Disadvantages of Light Microscopes
Depth of Field is Restricted.Resolution is limited to 200nm (about half the wavelength of light) Magnification Limited to x1500
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Advantages of Electron Microscopes
Greater Depth of Field can be observed. Higher Magnification (up to X500,000), Greater Resolution (can distinguish between objects 0.2nm apart)
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Disadvantages of Electron Microscopes
Expensive to buy, Expensive to run when generating electron beam, Preparing Specimens is a complex procedure, Images Black/White, Living Specimens cannot be observed
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Units of Measure
1mm = 1000micrometres=1000,000 nanometres
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Measuring the Length of Specimens
You have 2 Scales; A eyepiece graticule and a stage Micrometer. The eyepiece graticule changes with the lens magnification, so it has to be calibrated with the stage micrometer. (for each lens size)
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How to do this
Stage Micrometre=1mm/1000micrometre, divided into 100 divisions so 1 division=10microm. Then match up the some eyepiece units to the s.d, for instance 10e.p.u might equal 25 s.d }You know that 1s.d=10microm so 25x10=25s.d=250microm, (next slide)
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continued...
this is equal to 10 E.P.U, so to work out 1 E.P.U we divide 250microm by 10, so 1 E.P.U = 25microm.
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Other cards in this set

Card 2

Front

What Are the Different Type of Microscopes?

Back

There are 2 Main: Light and Electron, However Electron Microscopes have 2 different types: Transmission Electron Microscope (TEM) and Scanning Electron Microscope

Card 3

Front

What are the Differences between TEM AND SEM?

Back

Preview of the front of card 3

Card 4

Front

Advantages of Light Microscopes

Back

Preview of the front of card 4

Card 5

Front

Disadvantages of Light Microscopes

Back

Preview of the front of card 5
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