scanning electron microscope (SEM), an instrument similar to an electron microscope in that a beam of electrons is used to scan the surface of a specimen. The beam is moved in a point-to-point manner over the surface of the specimen. These electrons are deflected, collected, accelerated, and directed against a scintillator. The large number of photons thus created are converted into an electric signal that, in turn, modulates the beam scanning the surface of the specimen. The image produced appears to be three-dimensional and lifelike. Compare electron microscope, transmission scanning electron microscope.
