Biology Ease Staff asked 2 years ago
In TEM a finely focussed beam of electrons from an electron gun is passed through a specially prepared ultra-thin section of the specimen. The beam is focused on a small area of the specimen by an electromagnetic condenser lens. The specimen to be observed is placed on a copper mesh grid. Finally, the electrons are focussed by an electromagnetic projector lens (instead of an ocular lens as in a light microscope) on a screen or photographic plate.
The final image in a TEM is known as a transmission electron micrograph.
The salts of some heavy metals, e.g., lead, osmium, tungsten, and uranium are often used for staining. These heavy metal stains are used to increase the contrast between ultrastructures and the background. The metals can be fixed onto the specimen and are referred to as positive staining while if used to increase the opacity of the surrounding field it is called negative staining.
