Quantum theory

Quantum theory. Physical theory based on the use of the concept of quantum unit to describe the dynamic properties of subatomic particles and the interactions between matter and radiation . It is one of the fundamental pillars of current Physics.


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  • 1 History
  • 2 Booster of quantum theory
  • 3 Meaning of quantum mechanics
  • 4 Einstein’s contributions to this theory
  • 5 Importance of quantum mechanics
  • 6 Achievements
  • 7 Sources


In the 18th and 19th centuries , Newtonian or classical mechanics seemed to provide a totally accurate description of the movements of bodies, such as planetary motion. However, in the late nineteenth and early twentieth centuries, certain experimental results cast doubt on whether Newtonian theory was complete. The new observations included lines that appear in light spectra emitted by heated gases or subjected to electric shocks . Based on the model of the atom developed in the early 20th century by the New Zealand- born British physicist Ernest Rutherford , in which negatively charged electrons revolve around a positive nucleus, in orbits dictated by Newton’s laws of motion , scientists expected electrons to emit light in a wide range of frequencies, and not in narrow bands. frequency that form the lines of a spectrum.

Propeller of quantum theory

The foundations of the theory were laid by the German physicist Max Planck , who in 1900 postulated that matter can only emit or absorb energy in small discrete units called quanta. Another fundamental contribution to the development of the theory was the uncertainty principle, formulated by the German physicist Werner Heisenberg in 1927 , and which states that it is not possible to specify exactly the position and linear momentum of a subatomic particle simultaneously.

Meaning of quantum mechanics

According Schrödinger the wave mechanics and matrix mechanics are different versions of the same mathematical theory, now called quantum mechanics. Even in the case of the atom of hydrogen , formed by only two particles, both interpretations mathematics are very complex. The next simplest atom, helium , has three particles, and even in the relatively simple mathematical system of classical dynamics, the problem of three bodies (the description of the mutual interactions of three different bodies) cannot be solved by full. However, it is possible to calculate energy levels. By applying quantum mechanical mathematics to complex situations, physicists can employ one of the many mathematical formulations. The choice depends on the convenience of the formulation to obtain appropriate approximate solutions.

Einstein’s contributions to this theory

Albert Einstein used the concept of the quantum introduced by Planck to explain certain properties of the photoelectric effect , an experimental phenomenon in which a metallic surface emits electrons when radiation hits it. According to classical theory, the energy of the emitted electrons measured by the electrical voltage they generate should be proportional to the intensity of the radiation. However, it was found that this energy was independent of the intensity that only determined the number of electrons emitted and depended exclusively on the frequency of the radiation.

The higher the frequency of incident radiation, the higher the energy of the electrons; below a certain critical frequency, no electrons are emitted. Einstein explained these phenomena by assuming that a single quantum of radiant energy expels a single electron from the metal . The energy of the quantum is proportional to the frequency , so the energy of the electron depends on the frequency.

Importance of quantum mechanics

The quantum mechanics solved all the major problems that troubled physicists in the early years of the twentieth century . It gradually expanded knowledge of the structure of matter and provided a theoretical basis for understanding atomic structure and the phenomenon of spectral lines: each spectral line corresponds to the emission or absorption of an energy quantum or photon , when an electron experiences a transition between two energy levels. The understanding of chemical bonds was radically altered by quantum mechanics and was based on the Schrödinger wave equations. The new fields of physics , such asSolid state physics , condensed matter physics, superconductivity , nuclear physics, or elementary particle physics – have relied heavily on quantum mechanics .


Since 1925 no fundamental deficiencies have been found in quantum mechanics, although it has been debated whether or not the theory should be considered complete. In the 1930s , the application of quantum mechanics and special relativity to electron theory allowed British physicist Paul Dirac to formulate an equation involving the existence of the electron spin . It also led to the prediction of the existence of the positron, which was experimentally verified by the American physicist Carl David Anderson . The application of quantum mechanics to the field of electromagnetic radiationHe managed to explain numerous phenomena such as braking radiation (emitted by electrons braked by matter) and the production of pairs (formation of a positron and an electron when electromagnetic energy interacts with matter). However, it also led to a serious problem, the so-called divergence difficulty: certain parameters, such as the so-called naked mass and naked charge of electrons, appear to be infinite in Dirac’s equations . This difficulty was partially solved in 1947 – 1949 within the framework of a program called renormalization, developed by the Japanese physicist Shin’ichirō Tomonaga.American physicists Julian S. Schwinger and Richard Feynman, and British-American physicist Freeman Dyson . In this program, the naked mass and charge of the electron are taken as infinite so that other infinite physical quantities are canceled out in the equations. Renormalization greatly increased the precision in calculating the structure of atoms from the fundamental principles.


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