Microscopes

Magnification and Resolution

Magnification - How large the image is compared to the actual size of the specimen.

Resolution - How detailed the image is, and how well the microscope distinguishes between two point that are closed together.

Units -

1000mm - 1m           1000 (Micrometres) - 1mm               1000 (nanometres) - 1 (micrometre)

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Light Microscope

  • Uses light and several lenses to magnify a sample.
  • Light from condenser lense - this passes through a specimen - certain wavelenghts filtered to produce an image.
  • Objective lense - can focus and can change magnification.
  • Eye piece lense - altered to change magnification.

Max magnification - 1500 x

Max Resolution - 200 nm (wavelength light)

USES - IDENTIFY DIFFERENT BACTERIA TYPES

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Transition Electron Microscopes (TEM)

  • Have lower wavelengths of light - produce an image - higher resolution

Disadvantages - Operation requires training, false colour image, thin specimen, specimen are dead.

Advantages - Most powerful microscope, high quality detailed image.

Max resolution - 1nm

Magnification - x 500,000

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Scanning Electron Microscopes

  • Electromagnetic coils - electron beam back and forth - scanning specimen.
  • Electrons bounce - off specimen and are directed at a screen - this creates an image.

Advantage - Sharp 3D images

Disadvantage - Less powerful that TEM, false colour imaging, only dead specimen

Max resolution - 1nm

Magnification - x 200,000

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