Microscopy
- Created by: emilytester
- Created on: 07-04-14 16:10
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- Microscopy
- Magnification and Resolution
- Magnification is how many times larger an image is than the object itself.
- Resolution is the degree to which it is possible to distinguish between 2 objects. (The higher the resolution - the closer together you can distinguish between)
- Resolution for a light microscope - 200 nm
- Resolution for an electron microscope - 0.20 nm
- To investigate cells and their components you need both high magnification and high resolution.
- Light Microscopes
- How they work..
- 1. Use a number of lenses to produce an image that can be directly viewed at the eyepiece.
- 2. Light passes from a bulb under the stage, through a condenser lens and through the specimen.
- 3. The beam of light is focused through the objective lens and then through the eyepiece lens.
- Advantages of the light microscope
- A wide range of specimens can be viewed with a light microscope including living organisms.
- Disadvantages of the light microscope
- Most light microscopes are only capable of magnification up to 1500x
- Objects closer than 200nm apart will only be seen as 1 object
- Preparation of specimens for light microscopy...
- 1. STAINING - coloured stains are chemicals that bind to chemicals in/on the specimen so they can be seen.
- 2. SECTIONING- specimens have been embedded in wax so thin sections can be cut without distorting the structure of the specimen.
- Measuring cells and organelles found with a light microscope...
- A microscope eyepiece is fitted with a graticule with is transparent with a small ruler etched on it.
- The graticule represents different lengths at different magnifications.
- Calibration of the eyepiece graticule: 1) a microscopic ruler on a special slide (A STAGE MICROMETER) is placed on the stage. 2) this ruler is 100mm long and divided into 100 divisions.
- How they work..
- There is a relationship between actual size, magnification and image size..
- IMAGE SIZE = ACTUAL SIZE x MAGNIFICATION
- Electron Microscopes
- Transmission Electron Microscopes
- Scanning Electron Microscopes
- Magnification and Resolution
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