ABSTRACT
In light microscopy, a beam of light is focused through a microscope using glass lenses to produce an enlarged image of the specimen. The specimen to be viewed is first fixed with alcohol or formaldehyde, embedded in wax and then cut into thin sections. A section is illuminated from below with the beam of light being focused on to it by the condenser lens. The incident light that passes through the specimen is then focused by the objective lens on to its focal plane, creating a magnified image. In dark-field microscopy, light from the condenser lens is directed at an angle on to the specimen such that only light which has been refracted or diffracted by the specimen enters the objective lens and forms an image. In electron microscopy, a beam of electrons is focused using electromagnetic lenses. The specimen is mounted within a vacuum so that the electrons are not absorbed by atoms in the air.
