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In 1859, Gustav Kirchhoff discovered that the energy and temperature emitted from the blackbody were related to frequency. So he wrote down a formula: EpistJ (Tgravev), where T is the temperature and v is the frequency. Then he challenged the physicist to find the function J.

Twenty years later, Joseph Stefan carried out a large number of experiments, and based on these experiments, it is proposed that the total energy emitted by the hot body is proportional to the fourth power of the temperature E ∝ T powers. Five years later, Ludwig Boltzmann came to the same conclusion using thermodynamics and Maxwell's electromagnetic theory completely independently. Today, we know that the result of these two ideas is the famous Stefan-Boltzmann law. The problem is that it does not fully answer Kirchhoff's challenge because it does not solve the problem of specific wavelengths.

In 1896, William Wayne put forward a theoretical formula for the distribution of radiation intensity according to wavelength. The experimental results show that his theory matches very well for the case of short wavelength. However, for the case of long wavelength, the theory deviates greatly from the experiment. When Max Planck saw the results of the experiment, he made a bold guess that the total energy was made up of indistinguishable quantum energy, so that his theory could explain the results. However, he is not entirely satisfied with his conjecture because he feels that the theory has no realistic basis.

In 1905, Einstein put forward the quantum theory of light on the basis of photoelectric effect experiments. The experimental results of photoelectric effect are not consistent with classical electromagnetism, which predicts that continuous light waves transfer energy to electrons. When electrons accumulate enough energy, electrons will be emitted. If the light intensity changes, the kinetic energy of the emitted electrons should theoretically change. If the light source is dark enough, it should cause emission delay.

However, experiments show that electrons will be emitted only when the light exceeds a certain frequency, regardless of the intensity of the light or the duration of the exposure. This shows that light cannot be seen as a simple wave, but as a group of discrete packets called photons. Einstein realized that the energy change occurs in the transition of the quantum material in the oscillator, where the energy change is a multiple of hv, h is the Planck constant, and v is the frequency of light.

In 1913, Niels Bohr proposed a new atomic model and used the idea of quantization to explain the spectral lines of hydrogen. In his model, a hydrogen atom is depicted as a positively charged nucleus surrounded by a negatively charged electron. Electrons can only exist in specific positions or orbits determined by their angular momentum, which is limited to an integral multiple of the reduced Planck constant, and the emission line can be explained by the transition of electrons between orbitals.

From Planck's quantum theory to Bohr's atomic model, they can explain many experimental results. But the problem is that these theories are not derived from the first principle, and there is no reason to explain why quantization occurs.

In 1923, Louis de Broglie proposed a theory that allows particles to exhibit wave properties and waves to show particle properties. Two years later, in 1925, Werner Heisenberg proposed a treatment based on discussing only the electronic behavior of observable quantities (that is, the frequencies of atoms and light). Based on this, Marx born made a leap, and the classical variables of position and momentum will be represented by a matrix. Then Erwin Schrodinger proposed an equation that treats electrons as waves. Born found that the way to explain the wave function that appears in the Schrodinger equation is to use it as a tool for calculating probability.

In 1927, Heisenberg developed an early version of the uncertainty principle, which he created by analyzing a thought experiment. In this thought experiment, he tried to measure the position and momentum of electrons at the same time. But at this time, he did not give a definition of the actual meaning of uncertainty in the measurement. In the same year, Paul Dirac made an incredible leap in unifying quantum mechanics and special relativity by proposing the Dirac equation of electrons. It realizes the relativistic description of the electron wave function that Schrodinger could not obtain, and it also predicts the existence of electron spin and antimatter.

This article comes from the official account of Wechat: Vientiane experience (ID:UR4351), author: Eugene Wang

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