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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.
    • There is a relationship between actual size, magnification and image size..
    • Electron Microscopes
      • Transmission Electron Microscopes
      • Scanning Electron Microscopes


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