This device is widely used in microbiology, various experiments, medicine, laboratory, and many more. Then in 1931, Ernest Ruska, a German physicist, invented the electron microscope. But it was not possible to describe the structure of an object with a diameter less than 0.2 mm. This microscope accurately describes the smallest part of an object.Īfter the invention of the microscope, the structure of the object from 0.2 mm could be described using an optical microscope. It is of two types based on its structure such as transmission electron microscope and Scanning electron microscope (SEM). The electron microscope is a breakthrough invention in microbiology. The darker areas of the image represent those areas of the sample that fewer electrons were transmitted through (they are thicker or denser).A microscope is used to see objects that are not visible to the naked eye.

The image strikes the phosphor image screen and light is generated, allowing the user to see the image.

The image is passed down the column through the intermediate and projector lenses, being enlarged all the way.

Optional Objective and Selected Area metal apertures can restrict the beam the Objective aperture enhancing contrast by blocking out high-angle diffracted electrons, the Selected Area aperture enabling the user to examine the periodic diffraction of electrons by ordered arrangements of atoms in the sample.

This transmitted portion is focused by the objective lens into an image.

The beam strikes the specimen and parts of it are transmitted.

The beam is restricted by the condenser aperture (usually user selectable), knocking out high angle electrons (those far from the optic axis, the dotted line down the center).

The second lens(usually controlled by the 'intensity or brightness knob' actually changes the size of the spot on the sample changing it from a wide dispersed spot to a pinpoint beam. The first lens(usually controlled by the 'spot size knob') largely determines the 'spot size' the general size range of the final spot that strikes the sample. This stream is focused to a small, thin, coherent beam by the use of condenser lenses 1 and 2.The 'Virtual Source' at the top represents the electron gun, producing a stream of monochromatic electrons.A more technical explanation of a typical TEMs workings is as follows (refer to the diagram below): Whatever part is transmitted is projected onto a phosphor screen for the user to see. TEMs work the same way except that they shine a beam of electrons (like the light) through the specimen(like the slide). This transmitted beam is then projected onto the viewing screen, forming an enlarged image of the slide. These effects result in only certain parts of the light beam being transmitted through certain parts of the slide. A projector shines a beam of light through (transmits) the slide, as the light passes through it is affected by the structures and objects on the slide.

Morphology The size, shape and arrangement of the particles which make up the specimen as well as their relationship to each other on the scale of atomic diameters.Ĭrystallographic Information The arrangement of atoms in the specimen and their degree of order, detection of atomic-scale defects in areas a few nanometers in diameter Compositional Information (if so equipped) The elements and compounds the sample is composed of and their relative ratios, in areas a few nanometers in diameterĪ TEM works much like a slide projector. TEMs are patterned after Transmission Light Microscopes and will yield similar information. Transmission Electron Microscope Transmission Electron Microscope (TEM)

Parts transmission electron microscope