The electromagnetic radiation emitted by black bodies being, at a specific temperature, in thermal equilibrium, is covered by Planck's law.
Planck's law is a widely used, important and necessary content in the field of physics . It bears, in its name, the surname of a prominent physicist and professor of German origin named Max , to whom we owe the discovery of Planck's constant , for example. In recognition of his valuable contributions (especially for his contributions in theory or quantum mechanics ), this figure born in 1858 and died in October 1947 was awarded, in 1918, the Nobel Prize in Physics .
It should be noted, as a synthesis to later incorporate information, that this principle refers to the intensity of black body radiation . In this framework, the temperature reached by a black body is key since it affects the frequency spectrum , which climbs to higher values depending on the thermal increase: above five hundred degrees Celsius, specifically, a black body reaches emit a large amount of visible light . An exposure at room temperature, meanwhile, causes the emission, almost entirely, to be located in the infrared zone of the so-called electromagnetic spectrum .
It is also interesting to note that Planck's law has points of contact and links with both the law of displacement, approximation or Wien formula and with the Stefan-Boltzmann law (oriented to the total hemispheric emissive power of the thermal radiation emitted for a black body ). In the limit range of low frequencies, however, there are coincidences between it and the Rayleigh-Jeans law or formula .
Key concepts of Planck's law
To understand in depth what Planck's law consists of and to be able to apply it appropriately, it is essential to be clear about the definition of several key concepts.
It is essential to know, first of all, what and how a black body is. This expression, as noted when reviewing the theory, refers to a physical body of an ideal nature capable of completely absorbing, regardless of the angle of incidence and the frequency it has, the incident electromagnetic energy . This absolute absorption that traps each of the colors that reach the surface explains why the body is considered “black” . As a result of this phenomenon, thermal radiation also arises. The work of the physicist Gustav Robert Kirchhoff (whose birth occurred in 1824 and his death in 1887) was extremely relevant to advance the segment of quantum theory based on the knowledge accumulated about black body radiation .
By learning about it, it is possible to estimate the energy emitted by stars and planets even if they are not in thermal equilibrium . Knowing the particularities of black bodies, it can be established that black holes appear in this category (with an almost perfect range), whose mass influences the emission at a certain temperature of that identified as Hawking radiation .
Finally, it is enriching to learn about the quantization of energy , a phenomenon that allows us to understand and discover numerous typical properties of atoms. Taking advantage of the contributions of Planck (a surname that is also recognized in the unit defined as Planck time and in Planck length ) on this topic, Albert Einstein was able to offer an explanation of the photoelectric effect (a phenomenon detected by the German physicist Heinrich Hertz but explained on a theoretical level by Einstein , the promoter of the world-famous theory of relativity ).
Max Planck and Albert Einstein were outstanding figures in science whose professional contributions complemented each other.
Applications
Planck's law is applied in multiple areas, research and disciplines, as it emerges from reality.
For cosmology experts, to indicate a specific case, it is used to study cosmic background radiation (essential when wanting to appreciate traces of the Big Bang , the colossal explosion that marked the beginning of the universe), while in classical physics it has emerged as a solution to a failure, related to electromagnetism , which has been dubbed the ultraviolet catastrophe . It is decisive, even, for the sun's own emission spectrum .
Also, say those who master the subject, it is of interest in the field of spectroscopy and is a great ally of the experimental measurements carried out by those dedicated to astrophysics and is important for technological developments, to add other references.
Max Planck did a great job in giving impetus to quantum mechanics.
Planck's law and quantum theory
At the end of 1900, months after Max Planck found the spectral law of black body radiation that came to light a season later, Planck's constant was presented at the German Physical Society (useful for determining what is the energy that a photon has).
The popularly called Planck's law , over time, became one of the pillars of quantum theory . In this context, the idea of an electromagnetic energy that was quantized , segmented into a series of units of discrete order, mentioned as quanta, gained strength.