Optical microscopes cannot magnify more than about 2500 times because the light rays can not produce a sharp image. The electron microscope is such a powerful instrument which can magnify minute objects by as much as a million times. It is used to study micro-organisms such as viruses, tissues and bacteria. We know that light travels in the form of waves. Similarly, waves are also associated with the moving electrons. These are known as matter waves. Electron microscope was constructed by making use of matter waves associated with electrons. Wavelengths of light waves are longer than that of the waves associated with electrons. Due to this reason an electron microscope has a higher resolving power and greater magnifications as compared to an optical microscope.
The electron microscope works like an optical microscope with a condenser and objective and eyepiece (projector) lenses. The lenses are powerful magnets or electrodes.
In an electron microscope a beam of electrons is focussed onto the object. With the help of electromagnetic lenses an enlarged image of the object is produced on a fluorescent screen. This image is photographed on a photographic film or plate. With the help of this photograph the object structure is studied in detail. Most of the big research laboratories make use of electron microscopes.