Working Principle of Electron Microscope

Electron microscopes are designed to provide information about a sample’s structure, morphology, and composition by detecting signals that result from the interaction of an electron beam with the sample.

• The electron gun creates electrons.
• Two sets of condenser lenses concentrate the electron beam on the specimen and then into a slim, focused beam. To propel electrons along the column, an accelerating voltage (usually between 100 kV-1000 kV) is applied between the tungsten filament and the anode.
• The specimen being analyzed is exceptionally thin, at a thickness of at least 200 times less than that used in the optical microscope.
• The specimen holder is already equipped with ultra-thin sections measuring 20-100 nm.
• When the electronic beam passes through the specimen, electrons scatter in different directions, influenced by the specimen’s thickness or refractive index. The more electron-dense regions in the specimen scatter more electrons, resulting in a darker appearance in the image since fewer electrons reach that area of the screen. Conversely, transparent regions appear brighter.
• The electron beam emanating from the specimen travels to the objective lens, which boasts high magnification power and generates an intermediate magnified image.
• Subsequently, the ocular lenses produce the final, further magnified image.

The diagram of the electron microscope shows its complex internal components, including electron sources and electromagnetic lenses. There are two types of electron microscopes. The electron gun releases electrons that pass through multiple components and hit the gold-coated specimen. The diagram of an electron microscope with labels helps understand the various parts and their functions easily.

The well-labeled diagram of the electron microscope is given below: