Microscopy

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  • Microscopy
    • Microscopes produce a magnified image of a sample
      • Magnification = how much bigger the image is than the specimen
        • I = A x M  (Image Size = Actual Size x Magnification)
      • Resolution = how well a microscope distinguishes between two points that are close together
    • Two Types of Microscopes
      • 1) Light Microscopes
        • Use Light
        • They have lower resolution
          • Maximum = 0.2 micrometers
        • Maximum Magnification = x1500
    • Staining
      • Samples stained as a result of specimen being transparent
        • Electrons pass straight through it
      • For LIght Microscopes use dye
        • Common stains are methylene blue and eosin
          • Stain is taken up by some parts of the specimen more than others
            • Contrast makes the different parts show up
      • For Electron Microscopes
        • Objects are dipped in solution of heavy metals e.g. lead
          • Metal ions scatter electrons
            • Gain Contrast
  • 2) Electron Microscopes
    • Use electrons
    • Higher resoclution, so giove more detailed images
    • Two Types of Microscopes
      • 1) Light Microscopes
        • Use Light
        • They have lower resolution
          • Maximum = 0.2 micrometers
        • Maximum Magnification = x1500
    • Two Types
      • TEM - Transmission
        • Use Electromagnets to focus a beam of electrons
          • Electrons transmitted through specimmen
            • Denser parts absorb more electrons, makes them look darker
        • Advantege - provide high resolution images
        • Bad as they can only be used on thin specimens
      • SEM - Scanning
        • Scan a beam of electrons across specimen
          • Knocks off electrons already on specimen
        • Advantages - images produced show the surface of the specimen and can be in 3D
        • Give lower resolution than TEM

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