Thermal radiation (radiation) is the transfer of thermal energy, represented by electromagnetic waves, from one body to another. It arises due to the internal energy of a given body. In this case, the wavelength ranges from 0.74 to 1000 micrometers. Waves that have a specific length are absorbed by the body and then pass through the atmosphere. It is interesting that radiation can occur not only in a certain environment, but also in a vacuum. This process releases heat - a unit of energy.
Thermal radiation can occur as a result of chemical or nuclear reactions, electromagnetic scattering, as well as during mechanical action on an object. In this case, the energy that is released can be transmitted by touching, that is, the interaction between objects with high and low temperatures, as well as by transfer using liquids or gases, or radiation (heat transfer from a source to matter). The latter method is productive enough to produce heat. Thermal rays carry energy and when they hit an object, this energy is absorbed - and the objects heat up. When two objects in contact with different temperatures are in contact with each other, a heat flow is generated, which stops when the temperatures of the bodies are compared. Thus, thermal radiation occurs. This process can occur in nature, for example, in the atmosphere, and artificially, for example, in an incandescent lamp.
It should be noted that each body reproduces continuous radiation and absorbs the radiation of other bodies. In the case when there is thermal equilibrium, for each object the flux of radiated and absorbed radiation will be the same. In this case, we can talk about the absence of heat exchange processes between the elements. When the temperature of one element is higher than that of the other, the first will radiate thermal energy to a greater extent than absorb it from another body. Here we can talk about the presence of heat transfer between the elements.
Consider what constitutes thermal radiation and its characteristics.
It is known that elements that are heated to a high temperature glow. This phenomenon is called thermal radiation. It is accomplished by the movement of molecules of a substance having a temperature above zero. So, at high temperature short visible waves are emitted, at low - long infrared.
Consider this phenomenon as an example. So, living quarters in most cases are heated by electric heat emitters. In this case, the red glow of the spirals is the visible thermal radiation. And infrared radiation carries heat, which heats this room.
Thermal radiation is a type of radiation that is equilibrium, that is, does not change macroscopic parameters. All other types of radiation are nonequilibrium.
The essence of all the rays is the same. It is presented in the form of propagating electromagnetic waves in space. Thermal energy is generated as a result of the generation of the internal energy of a heated element. Moreover, the amount of this kind of energy depends on the temperature and physical properties of the body that emits it.
Thermal radiation plays an important role in natural processes and human life. The sun is the most powerful heat emitter. The intensity of thermal radiation is approximately 1.3 W / m2.
Thus, in thermodynamic equilibrium, all elements of the system have the same temperature. The energy of thermal radiation that comes from each body is offset by the energy that is absorbed by this body. Such a process is called equilibrium thermal radiation.