What is the working principle of electron microscope?

Answer 1

An electron microscope is a magnifier that uses electrons to enlighten the subject and display a magnified image. The electron microscope has a greater amount of resolution as compared to other microscopes. Using this, smaller objects can be seen with a naked eye as they have lesser wavelength than light, hence it has a very strong resolving power to view the object in a larger picture. In this article, we would be taking a look at how does an electron microscope work? Before answering how does the electron microscope work, you must know that there are mainly two types of microscopes. One is a Transmission Electron Microscope (TEM), and the other is the Scanning Electron Microscope (SEM). Let us first understand how an electron microscope works? The TEM was the first ever electron microscope and it was used to see within the cells. The TEM allows only those electrons to be viewed which pass through the subject, which obviously means that only those electrons which pass through the sample may be seen. This gives rise to black/white and shades of gray on the finished picture. The electron is a pin-shaped cathode, heated to an extent which induces a beam of electrons to be developed. The empty space that resides within the microscope then makes the electron ray to move into the condenser. The condenser is an electromagnet that concentrates on the electron rays onto the object. Then the electrons are averted off when they hit the areas of the object. This is due to the object being smeared with weighty metals, which will be imbibed by particular portions of the cell that will then bend the electrons in a different manner and allow the quite visible contrasts within the cell. The Projective which is nothing but a series of lens-arrangements, then focuses the leading electron beam onto a fluorescent shield where a black and white picture is generated. It is used when only the surface of the object is to be viewed as in this case the image is generated from the reflected electrons.

Answer 2

The basic steps involved in all EMs:

A stream of electrons is formed (by the Electron Source) and accelerated toward the specimen using a positive electrical potential.

This stream is confined and focused using metal apertures and magnetic lenses into a thin, focused, monochromatic beam.

This beam is focused onto the sample using a magnetic lens

Interactions occur inside the irradiated sample, affecting the electron beam.

These interactions and effects are detected and transformed into an image.

At the end of the 19th Century, it was realized by physicists that the only way to improve on the light microscope was to use radiation of a much shorter wavelength. J.J. Thompson in 1897 discovered the electron; others considered its wave-like properties. In 1924, Louis deBroglie demonstrated that a beam of electrons traveling in a vacuum behaves as a form of radiation of very short wavelength, but it was Ernst Ruska that made the leap to use this wave-like properties of electrons to improve on the light microscope.

Today there are two major types of electron microscopes; the transmission electron microscope (TEM) and the scanning electron microscope (SEM)

TEM: magnifies 50 ~ 1 million times

the specimen appears flat

SEM: magnifies 5 ~ 500,000 times

sharp images of surface features

In the TEM, the electrons from the electron gun pass through a condenser lens before encountering the specimen, close to the objective lens. Most of the magnification is accomplished by the intermediate and projector lenses. The image is viewed through a window at the base of the column and photographed by raising a hinged screen.

In the SEM, electrons from the electron gun are focused to a fine point at the specimen surface by means of the lens system. This point is scanned across the specimen under the control of currents in the scan coils situated within the final lens. Secondary electrons are emitted from the specimen surface and are attracted to the detector. The detector relays signals to an electronic console, and the image appears on a television screen.

Answer 3

Light Microscope: the specimen is mounted on a plate. A bulb emits light from under the plate, light that goes through the preparation and into the lense, in which an image is formed. Electron transfer microscope: the specimen is placed in the middle of a device that has an "electron gun". The preparation is "shot" with electrons which go through the preparation and land on a receiving plate which, based on the uptake of electrons by the preparation, creates a picture of the specimen.

Answer 4

In a vacuum it is possible to produce waves of electrons that behave very much like light-waves: you just have to regulate frequency. These electric waves bounce off of objects just like light waves do, can be directed and focused by electrostatic and magnetic fields to be enlarged. These are sensed by a grid of electron detectors mimicking a retina that turn an electron strike into an electric current which then of course can be used to produce an image.

Answer 5

In fluorescence microscopy, the sample you want to study is itself the light source. The technique is used to study specimens, which can be made to fluoresce. The fluorescence microscope is based on the phenomenon that certain material emits energy detectable as visible light when irradiated with the light of a specific wavelength. The sample can either be fluorescing in its natural form like chlorophyll and some minerals, or treated with fluorescing chemicals.

Answer 6

The working principles of electron microscopes by utilizing wavelengths and achieving resolution and magnifications up to approximately 10,000,000x. Electron microscopes use electron beams to highlight specimens and produce magnified images.

Answer 7

Each concave lens bends light to make the object appear larger.

Answer 8

An optical microscope uses visible light and a system of lenses to magnify images of small samples. There are some that include functions that improve resolution and sample contrast.

Answer 9

It work by providing strinking three-dimensional images.