microscopes topic

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  • Microscopes topic
    • eukaryotic cells
      • cells containing a true nucleus as a linear DNA existing as chromosomes
    • prokaryotic cells
      • cells that lack a true nucleus- circular strand in the cytoplasm
    • light microscopes
      • uses glass lenses to refract light waves to produce a magnified image of the object
        • specimen used needs to be thin and transparent to allow light waves to pass
        • works by:focusing light onto specimen using condenser lens,light passes through specimen
          • light then captured and refracted by the objective lens
            • light waves travel up to the eye piece lens creating the final image
      • staining: used to bind to parts of the specimen and not others,giving contrast between different parts of the specimen,allowing structures to be seen more easily
    • magnification
      • image size/real size
    • resolution is theability to distinguish between two objects that are close together
    • electron microscopes
      • use beams of electrons (shorter than light waves) which means it gives a higher resolution (0,5nm)
      • series of electromagnets focus electrons onto specimen
        • where electrons hit the screen is bright, where they don't is dark
          • black and white image formed
      • transmission electron microscope
        • specimen stained with heavy metal salts
          • where the stain is not taken up the electrons will pass through,giving contrast
            • 2D image formed, max mag 500,000x, resolution- 0,5nm
      • scanning electron microscope
        • bounces electron beams off surface of the specimen
          • gives a 3D surface image with max mag:300,000x and resolution:0,2nm


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