Introduction to the Year of Science or Why is the glass transparent?
In Belarus, passes # GodNavuki!
You should not rejoice, because you will be Forced to find out this year A lot about modern Science! Recently, I conducted a survey - would you regularly like to learn something new about the structure of the World around you? And I was surprised when 83%! answered - Of course, YES !
So we still have time until the end of the year to make some Discoveries!
')
Discovery # 1
All materials are composed of atoms. The structure of the atom is such that it has a nucleus surrounded by electrons - and these very nuclei, surrounded by electrons, are arranged in a certain way inside the material. And it turns out that the atoms are too close to each other (at a distance of about 3 * 10-10 meters) and have too much influence on each other. In addition, there are a huge number of atoms in the material - there are about 10 to 22 degrees in one cubic centimeter ( 10,000,000,000,000,000,000 are just that ). Theoretically, it is possible and necessary (I would very much like) to know the exact value of the energy of each electron in the electric field of all other electrons (under rather difficult conditions, because there are too many of them), - But it is impossible to solve such a system of equations. Physicists have come up with how to roughly describe the behavior of all electrons in a crystal (and there are even more of them than atoms) - they invented Zone Theory and divided all electrons into two classes.
Valence electrons bound to atoms or involved in the formation of chemical bonds in a crystal have a lower energy value. And the conduction electrons (as if free) are able to move inside the crystal. From the point of view of modern physics, electrons cannot move absolutely freely, they are located at certain energy levels. The set of energy levels at which the valence electrons are located is the valence band, and the set of energy levels at which the free electrons are located is the conduction band. In addition, there are certain energy values that an electron cannot accept under any conditions — and all of these energy values (energy levels) are the Forbidden Zone.
And finally Discovery # 1 - it turns out that all materials can be divided into three types! (tell me if anyone knows why they don’t talk about it at school ..?) Dielectrics - semiconductors - metals! Just need to decide what this material is the size of the forbidden zone - if it is not, then it is a metal (a huge number of free electrons). If it is very small, then it is a semiconductor (only a small part of the electrons are free and in a pure semiconductor they are usually not enough to conduct current). And the materials in which the forbidden zone is large are dielectrics (they do not conduct current under any conditions).
If you want, then part of the electrons from the valence band can be transferred to the conduction band and greatly change the properties of the material. To do this, you need to either add atoms of a different type to the material or use some external influence (heat, light, etc.) that will give the electrons enough energy so that they can jump over the entire forbidden zone. The transition is possible only from the valence band to the conduction band and back - in the forbidden band the electrons cannot be located!
Discovery # 2
Once upon a time, Humankind (or rather only some of the people, because the rest was indifferent) learned that electricity and magnetism are interconnected and developed the theory of electromagnetic field and electromagnetic waves. Spent years ... a lot). And everyone seems to be happy and satisfied, and the radio works and the television, and much more. But more than 100 years ago, Max Planck came up with the hypothesis that light is emitted (or transferred) in small portions or quanta, which were later called photons. Later, Louis de Broglie extended this theory to the entire spectrum of electromagnetic waves. The joint works of Planck, Einstein, De Broglie, and others destroyed a coherent picture of the world and proved that any object in our world possessing any energy can be associated with a wave with certain parameters. And what is most important for us, any wave can be considered by physicists as a particle or an object with a certain energy.
A huge number of real experiments (and real applications) can be calculated and explained only using the concept of a wave for light or other electromagnetic waves - conventional optical devices (lenses, binoculars, microscopes), as well as radio, television, etc. BUT a huge number of experiments and applications explainable only with the use of particle-photons, which have a certain energy. There is no contradiction here, just physical theories are still far from claims to a complete description of the structure of the world.
Look at the spectrum of sunlight. The rainbow shows the part that we can see with the eye, the smaller part (47%). About 51% of the spectrum is shaded with light gray - this is infrared radiation, it warms us, but it is already impossible to see it with the eye.
We are already approaching the Discovery . It turns out that the relationship between energy and the wavelength that the Mighty Heap has established states that the longer the wavelength, the lower the energy of a quantum-photon particle. Conversely, the smaller the wavelength, the greater the energy - they are inversely proportional. The beautiful red arrow below shows exactly It, it is directed to the other side!
And what is there for tsiferki stand? It turns out that the energy of quantum-photon particles is usually measured in the same units as the world's most important value — the Width (value) of the Forbidden Zone of any material. I remind you that metals have 0 (zero), dielectrics have more than 3.5. And the fact that between 0 and 3.5 are semiconductors. As we see, the energy of light quanta in the visible wavelength region (the rainbow in the figure) has values from 1.5 to 3.0 - that is, less than the required values for absorption in glass (dielectric, which means the forbidden zone is more than 3.5 ), BUT can be perfectly absorbed by various semiconductors (silicon, germanium, gallium arsenide, etc.). And in the continuation of the Discovery, you can add - that in order to effectively absorb sunlight, you need to find or create such a material, whose bandgap width will allow you to absorb the maximum amount of sunlight.
Now we can try to answer, for example, the following question - Why are modern solar cells so ineffective?
You should not rejoice, because you will be Forced to find out this year A lot about modern Science! Recently, I conducted a survey - would you regularly like to learn something new about the structure of the World around you? And I was surprised when 83%! answered - Of course, YES !
So we still have time until the end of the year to make some Discoveries!
')
Discovery # 1
All materials are composed of atoms. The structure of the atom is such that it has a nucleus surrounded by electrons - and these very nuclei, surrounded by electrons, are arranged in a certain way inside the material. And it turns out that the atoms are too close to each other (at a distance of about 3 * 10-10 meters) and have too much influence on each other. In addition, there are a huge number of atoms in the material - there are about 10 to 22 degrees in one cubic centimeter ( 10,000,000,000,000,000,000 are just that ). Theoretically, it is possible and necessary (I would very much like) to know the exact value of the energy of each electron in the electric field of all other electrons (under rather difficult conditions, because there are too many of them), - But it is impossible to solve such a system of equations. Physicists have come up with how to roughly describe the behavior of all electrons in a crystal (and there are even more of them than atoms) - they invented Zone Theory and divided all electrons into two classes.
Valence electrons bound to atoms or involved in the formation of chemical bonds in a crystal have a lower energy value. And the conduction electrons (as if free) are able to move inside the crystal. From the point of view of modern physics, electrons cannot move absolutely freely, they are located at certain energy levels. The set of energy levels at which the valence electrons are located is the valence band, and the set of energy levels at which the free electrons are located is the conduction band. In addition, there are certain energy values that an electron cannot accept under any conditions — and all of these energy values (energy levels) are the Forbidden Zone.
And finally Discovery # 1 - it turns out that all materials can be divided into three types! (tell me if anyone knows why they don’t talk about it at school ..?) Dielectrics - semiconductors - metals! Just need to decide what this material is the size of the forbidden zone - if it is not, then it is a metal (a huge number of free electrons). If it is very small, then it is a semiconductor (only a small part of the electrons are free and in a pure semiconductor they are usually not enough to conduct current). And the materials in which the forbidden zone is large are dielectrics (they do not conduct current under any conditions).
If you want, then part of the electrons from the valence band can be transferred to the conduction band and greatly change the properties of the material. To do this, you need to either add atoms of a different type to the material or use some external influence (heat, light, etc.) that will give the electrons enough energy so that they can jump over the entire forbidden zone. The transition is possible only from the valence band to the conduction band and back - in the forbidden band the electrons cannot be located!
Discovery # 2
Once upon a time, Humankind (or rather only some of the people, because the rest was indifferent) learned that electricity and magnetism are interconnected and developed the theory of electromagnetic field and electromagnetic waves. Spent years ... a lot). And everyone seems to be happy and satisfied, and the radio works and the television, and much more. But more than 100 years ago, Max Planck came up with the hypothesis that light is emitted (or transferred) in small portions or quanta, which were later called photons. Later, Louis de Broglie extended this theory to the entire spectrum of electromagnetic waves. The joint works of Planck, Einstein, De Broglie, and others destroyed a coherent picture of the world and proved that any object in our world possessing any energy can be associated with a wave with certain parameters. And what is most important for us, any wave can be considered by physicists as a particle or an object with a certain energy.
A huge number of real experiments (and real applications) can be calculated and explained only using the concept of a wave for light or other electromagnetic waves - conventional optical devices (lenses, binoculars, microscopes), as well as radio, television, etc. BUT a huge number of experiments and applications explainable only with the use of particle-photons, which have a certain energy. There is no contradiction here, just physical theories are still far from claims to a complete description of the structure of the world.
Look at the spectrum of sunlight. The rainbow shows the part that we can see with the eye, the smaller part (47%). About 51% of the spectrum is shaded with light gray - this is infrared radiation, it warms us, but it is already impossible to see it with the eye.
And what is there for tsiferki stand? It turns out that the energy of quantum-photon particles is usually measured in the same units as the world's most important value — the Width (value) of the Forbidden Zone of any material. I remind you that metals have 0 (zero), dielectrics have more than 3.5. And the fact that between 0 and 3.5 are semiconductors. As we see, the energy of light quanta in the visible wavelength region (the rainbow in the figure) has values from 1.5 to 3.0 - that is, less than the required values for absorption in glass (dielectric, which means the forbidden zone is more than 3.5 ), BUT can be perfectly absorbed by various semiconductors (silicon, germanium, gallium arsenide, etc.). And in the continuation of the Discovery, you can add - that in order to effectively absorb sunlight, you need to find or create such a material, whose bandgap width will allow you to absorb the maximum amount of sunlight.
Now we can try to answer, for example, the following question - Why are modern solar cells so ineffective?
Source: https://habr.com/ru/post/373489/
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