Electron Microscope (principle, operation procedure, types, TEM, SEM, EM Images).pptx
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An electron microscope uses electron beams for illumination, achieving resolutions of 2-4 angstrom and magnifications up to 250,000 times. There are two main types: Transmission Electron Microscope (TEM), which creates images by transmitting electrons through a specimen, and Scanning Electron Microscope (SEM), which scans the surface to produce images based on emitted secondary electrons. While powerful, electron microscopes are expensive, require special conditions for operation, and cannot observe live specimens.
Electron Microscope (principle, operation procedure, types, TEM, SEM, EM Images).pptx
- 2. • An electron microscope is a microscope, which uses electron beams as a primary source of illumination. • An EM uses the same principles of an optical microscope but instead of photons or particles of light, it concentrates electrons onto an object. • The resolution of the electron microscope is between 2-4 Angstrom. It means that two points which are 2-4 Angstrom apart can be differentiated with the help of an electron microscope. • It makes the object 500X greater than the compound microscope and 250,000 greater than the naked eye.
- 3. Working Principle of Electron Microscope • Electrons are referred to as subatomic particles orbit around the atomic nucleus. When atoms are excited by the external heat energy, electron started to fly off from the atom. • In the electron microscope, a tungsten metal is heated with the help of a high voltage current, electrons form a continuous stream, which is used like a light beam. • The lenses used in EM are magnetic coils capable of focusing the electron beam on the specimen and illuminating it.
- 4. Operating Procedure of EM 1. The specimen is prepared 2. Now place the prepared specimen in the vacuum chamber. 3. Heat the electron gun to release beams of electron. 4. Use of coiled electromagnets instead of glass lenses to point the electron beam over the specimen. 5. After passing through the specimen the electron beam creates an image or electron micrograph, which is then viewed on a fluorescent screen rather than an eyepiece.
- 5. Types of Electron Microscope • There are two main types of electron microscope – 1. Transmission Electron Microscope (TEM) and 2. Scanning Electron Microscope (SEM).
- 6. 1. Transmission Electron Microscope (TEM) • TEM uses a high voltage electron beam to illuminate the specimen and create an image. • These electron beams are produced by an electron gun, which consists on a tungsten filament. • Then the electron beam is focused on the specimen by using electromagnetic condenser lens. • The transmitted electron beams are now magnified by the objective lens system of the microscope. • Now the magnified electron image is projected onto a fluorescent viewing screen to see the clear and magnified image of the specimen.
- 7. 2. Scanning Electron Microscope (SEM) • The heated electron gun releases a narrow electron beam. • These narrow electron beams will rapidly move over or scans the surface of the specimen. • As a result, this will emit a shower of secondary electrons and other types of radiations from the outer surface of the specimen. • The intensity of these secondary electron depends upon the shape and the chemical composition of the irradiated object. • These secondary electrons are collected by a detector, which helps to generate electronic signals. • These electronic signals are now scanned to produce an image. • The modern variants of SEM have the facility to record the photograph by digital camera. This microscope is used to observe the surface structure of microscopic objects.
- 8. Application of Electron Microscope
- 9. Advantages • Electron Microscopes can magnifies objects over 250,000 times. • It can resolve objects up to 200nm. • Electron Microscope allows us to investigate a greater depth of field. Disadvantages • Electron Microscopes are expensive. • Live specimens cannot be observed. • EMs are very large in size and must be operated in special rooms. • All images form in EM are in black and white. • Requires expertise to handle it.
- 10. Electron Microscope Images Pollen from a variety of common plants, colorized and magnified 500x.
- 11. A cell (red) heavily infected with SARS-COV-2 virus particles (yellow), isolated from a patient sample.