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Several basic concepts related to tem definition

Dec 25, 2015

     basic concepts related to tem definitio---Diffraction of light

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     Because the light has a wave,when light passes through a small hole, or a small hole light source, the optical system will produce a diffraction. The pattern is: the central part of a bright spot, in which there is a circle of light and shade, that is, (Airy) disc, the center of the energy of the light spot is about 84% of the incident light source.


     basic concepts related to tem definitio---Resolution

     Resolution has been called resolving power,it indicates that the instrument resolution enough to clearly separate the two or the centre of two particle minimum distance between skills.It is related to the nature of the light, that is, diffraction, interference, and lens aberrations.So to speak, the resolving power of the microscope is produced by the diffraction pattern of the central bright spot half resolution and resolution capability, it indicates that the instrument resolution enough to clearly separate the two or the centre of two particle minimum distance between skills. It is related to the nature of the light, that is, diffraction, interference, and lens aberrations. Can say, microscope resolution is diffraction center generated by the semi bright spot


     basic concepts related to tem definitio---Aberration and aberration of electron microscope

     Electron microscopy and light microscopy, due to the defects of the light source or lens,it can occur in a variety of aberrations or aberrations.


     basic concepts related to tem definitio---Contrast

     The human eye to distinguish objects, mainly according to the difference between objects of different parts or objects of light intensity and wavelength, these differences constitute the object contrast, also known as the "contrast".


     Due to the difference in the electron microscope specimen in different parts of the structure of matter, laxity is different, also differ in their electron scattering ability. As a result, through samples of electron beam generating density difference. The scattering of electrons, the number of small, and thus, the fluorescence screen on the excitation of fluorescence is weak, appear as a dark image; in contrast, the weak scattering ability of the place, the number of electrons through the screen, the excitation of light is strong, appear as bright as. 


     basic concepts related to tem definiti---Electromagnetic wavelength

     The electron flow in vacuum, which is relatively concentrated in high speed, is called an electron beam. The electron beam has the character of particle and wave, it can produce a certain wavelength of electromagnetic wave, the wavelength of the electron beam is completely depend on the acceleration voltage, the higher the voltage is, the shorter the wavelength is, the higher the resolution is.


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