Optical and Electron Microscopy
Optical and electron microscopy typically involves the diffraction, reflection or refraction of radiation.
They are used for the study and collection of the scattered radiation in order to build up an image.
This can be carried out by standard light microscopy, transmission electron microscopy or by scanning a fine beam over the sample as in confocal microscopy and scanning electron microscopy.
Scanning probe microscopy involves the interaction of the scanning probe with the surface or object of interest.
Optical or light microscopy involves the passing of visible light transmitted through or reflected from the sample through a single or multiple lenses to allow a magnified view of the sample. The resultant image can be detected visually or imaged digitally or on a photographic plate. The basic microscope is a simple staging area and support along with a single lens or a system of lenses, including attachments.
The technique of optical microscopy can only image dark or strongly refracting objects effectively. Diffraction will limit the resolution to 0.2 micrometers. Out of focus light from places outside the focal plane reduces the image clarity.
Live cells, for example, lack sufficient contrast to be studied as internal structures are often colorless and transparent. The best way to see these structures is to stain the different structures with selective dyes. This involves the killing of the cells and fixing the sample. Staining is not perfect and can produce artifacts, structural details that are caused by the processing of the specimen.