How Does An Electron Microscope Work?

Electron microscopes utilise the same main concepts that a light microscope uses. In light microscopy, you need: a light source, a specimen and a lens to magnify the image. Electron microscopy uses the same concepts, but with slightly different materials: electrons as the light source (these allow for a high resolution to be obtained), a specimen (frozen) and electromagnets replacing the lens (these focus the electron beams). First, a beam of electrons is fired through the sample. The electromagnets speed this beam up, causing the beam to act in a similar way to light waves. Another magnet then focuses the beam and produces the magnified image. There are two main types of electron microscopy: transmission (TEM) and scanning (SEM). TEM is used to investigate slices of biological specimens whilst SEM is used to examine the surface structure, due to a large depth of field. These are both vital in biomedical science, as they allow high resolution images of extremely small biological components to be seen e.g. the internal structure of mitochondria.