Microscope comparison

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  • Microscopes
    • Light Microscope
      • They are the oldest, simplest and widely used
      • Specimens are illuminated with light, which is focused using glass lenses. They are viewed using eyes or photographic film.
      • Specimens can be living or dead. However, they often need to be coloured to make them visible. Different stains, stain specific parts of cells.
      • Transmission light microscopes are most common. Light is transmitted through the specimen and is focused to form an image. They are good enough to see tissues and cells, but not smaller details such as cell organelles.
      • The problems of a light microscope are that the staining techniques could kill the microbes, there are also limitations to magnification and some light sources are hot and kill the microbes.
    • Electron Microscope
      • Uses a beam of electrons which illuminates the specimen. Electrons act like waves and can be produced easily, focused and detected.
      • The development revolutionised in the 1930s, allowing organelles like mitochondria to be seen in detail for the first time.
      • A beam of electrons have a wavelength of less than 1nm, which can be used to resolve small sub-cellular ultra structure
      • The problems are, there must be a vaccum inside, so it can't be used for living organisms. Also, specimens must be very thin so it can't be manipulated under the microscope. Specimens can also be damaged by the electron beam, so delicate molecules can be destroyed. Just like a light microscope, specimens must be stained so they are visible.
      • Transmission Electron Microscope
        • Work like a light microscope, transmitting a beam of electrons through a thin specimen. The electrons are then focused which forms an image on a screen/film.
      • Scanning Electron Microscope
        • Scan a fine beam of electrons onto a specimen. They are collected and scatter electrons by the surface. It has a poorer resolution, but gives an excellent 3-D images of surfaces/.


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