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
1. 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.
2. the sample may also be embedded in wax so thin sections can be cut without distorting the specimen
Transmission Electron Microscopes have a magnification of x500,000 and a resolution of 0.1nm
1. the electron beam passes through the sample; denser areas are harder to pass through, so this provides contrast and creates a 2D image
2. 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.
Scanning Electron Microscopes have a magnification of 100,000 and a resolution of 0.1nm.
1. the electron beam bounces of the sample and produces a 3D image
2. the sample must be placed in a vacuum because electrons will bounce of airbourne particles
3. lead salts may be used for staining in order to scatter electrons differently and gives contrast
Magnification = Image Size / Actual Size
1mm = 1000um

Resource summary

	Created by kin034 almost 10 years ago