Why electron microscopes shouldn't take the place of light microscopes
Electron microscopes use the principle of electron optics, replacing light beams and optical lenses with electron beams and electron lenses, so that the fine structures of substances can be imaged at very high magnifications. Although its resolving power is far better than that of optical microscopes, electron microscopes are difficult to observe living organisms because they need to work under vacuum conditions, and the irradiation of electron beams will also damage biological samples, so they cannot completely replace optical microscopes. Moreover, their cost is different, and the scope of work they are suitable for is also different. Hope my answer can help you.
Electron microscopes cannot completely replace optical microscopes for the following reasons:
1. Electron microscopes are optical microscopes with CCDs, display screens or computer accessories added to them. This can only be called a video microscope. During the entire imaging process, CCDs replace the human eye. Because in video imaging, electronic magnification is a virtual magnification, and in terms of pixels, photosensitive effects and other factors, it is too different from the human eye, so the effect is too different from that of a visual microscope;
2. There is another most important reason, CCD belongs to planar imaging, and human eyes, especially in the case of binocular observation, will produce a strong three-dimensional effect, which is the reason why the contrast effect of the two is too large;
3. Electron microscopes are mostly expressed as scanning electron microscopes. The effect of this kind of microscope is much better than that of ordinary optical microscopes, but because of its high price, it is rarely used in industry.
Why is the resolution of an electron microscope higher than that of a light microscope?
The magnification of the optical microscope is smaller than that of the electron microscope. The optical microscope can only observe microstructures, such as cells and chloroplasts, while the electron microscope can observe submicroscopic structures, that is, the structure of organelles, viruses, bacteria, etc.
The electron microscope projects an accelerated and concentrated electron beam onto a very thin sample, and the electrons collide with the atoms in the sample to change their direction, thereby producing solid angle scattering. The size of the scattering angle is related to the density and thickness of the sample, so images with different brightness and darkness can be formed, and the images will be displayed on imaging devices (such as fluorescent screens, films, and photosensitive coupling components) after zooming in and focusing.
Due to the very short de Broglie wavelength of the electron, the resolution of the transmission electron microscope is much higher than that of the optical microscope, which can reach 0.1-0.2nm, and the magnification is tens of thousands to millions of times. Therefore, the use of transmission electron microscopy can be used to observe the fine structure of samples, even the structure of only a single column of atoms, which is tens of thousands of times smaller than the smallest structure that can be observed by optical microscopy. TEM is an important analytical method in many scientific fields related to physics and biology, such as cancer research, virology, materials science, as well as nanotechnology, semiconductor research, etc.
