An electron microscope is a type of microscope that uses electrons to create an image of the specimen. The electrons are emitted from an electron gun and are accelerated by an electric field. They are then focused by a magnetic field into a beam that passes through the specimen. The resulting image is magnified by the lens system and projected onto a screen. Electron microscopes have much higher resolution than light microscopes, making them useful for investigating small objects such as viruses and bacteria.
There are two main types of electron microscope: transmission electron microscopes (TEMs) and scanning electron microscopes (SEMs). TEMs work by passing a beams of electrons through a very thin specimen, which casts a shadow on a photographic film or plate placed behind it. The shadow is magnified by the lens system and can be viewed using an eyepiece or photographed. SEMs work by scanning the surface of the specimen with a beam of electrons and detecting the resulting secondary electrons with detectors placed around the sample chamber. This produces an image that can be displayed on a monitor or printed out on paper.
Electron microscopes were first developed in the early 20th century and have since undergone many improvements. Today, they are used in scientific research, medicine, industry, and law enforcement. In recent years, advances in technology have led to the development of new types of electron microscope such as cold-field emission microscopes (CFEMs) and environmental SEMs (ESEMs). These new instruments offer improved performance for certain applications over traditional TEMs and SEMs