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OCR AS 1.1.1 - Microscopy
- Magnification - the degree to which the size of an image is larger than the object iteself
- Resolution - the degree to which it is possible to distinguish between
two objects in close proximity
- The Light Microscope has a magnification of x1500 and a resolution of 200nm
- Staining is used to help visualise cells and their
components by providing contrast. Different
chemicals will take up different amounts of the
stain so will appear different colours.
- the sample may also be embedded in wax so
thin sections can be cut without distorting the
specimen
- Staining is used to help visualise cells and their
components by providing contrast. Different
chemicals will take up different amounts of the
stain so will appear different colours.
- Transmission Electron Microscopes have a magnification of x500,000 and a resolution of 0.1nm
- the electron beam passes through the
sample; denser areas are harder to pass
through, so this provides contrast and
creates a 2D image
- Using electron microscopes means the sample must be cut into
very thin pieces using a diamond knife, embedding in resin,
removing the water from the sample and replacing with ethanol and
freezing it.
- the electron beam passes through the
sample; denser areas are harder to pass
through, so this provides contrast and
creates a 2D image
- Scanning Electron Microscopes have a magnification of 100,000 and a resolution of 0.1nm.
- the electron beam bounces of the sample and produces a 3D image
- the sample must be placed in a vacuum
because electrons will bounce of
airbourne particles
- lead salts may be used for staining
in order to scatter electrons
differently and gives contrast
- the electron beam bounces of the sample and produces a 3D image
- Magnification = Image Size / Actual Size
- 1mm = 1000um
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