THE wave-particle duality it is an inherent property of nature for both particles and waves. The dual nature can be observed through experiments when investigating the particle behavior, like electrons, protons, neutrons and even atoms. The wave-particle duality is the result of a large number of experiments and theories, such as those related to the photoelectric effect, clarified by Albert Einstein.
See too: Bosons, Fermions, Leptons – Standard Model of Particle Physics
Difference between wave and particle
Before talking about wave-particle duality, it is important to understand the characteristics of each of these aspects.
At particles:
- occupy a position in space,
- are endowed with mass,
- have a defined shape,
- they are well located, that is, their position can be easily determined.
already the waves:
- are disturbances in space,
- have no defined position,
- have no mass,
- are phenomena that transport energy,
- they are subject to the phenomena of reflection, refraction, diffraction, interference, etc.
Despite being totally different things, from the point of view of physics, every particle has a wave associated with it and vice versa. The way matter expresses itself, whether in wave form or particle form, is related to how it is observed.
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wave-particle duality
The wave-particle duality came to be questioned when the experimental results of Heinrich Hertz referring to the photoelectric effect got into direct contradiction to what was expected for the behavior of light, according to the electromagnetic theory of James Clerk Maxwell.
According to current theory at the time, any frequency of light should be able to eject electrons of a sheet metal, however, Hertz results showed that it was only from certain frequencies that such emission was detected.
THE explanation for the photoelectric effect was made by Albert Einstein, in 1905. Einstein showed that light behaved in a quantized way, that is, it was distributed in small “packets” of energy that stripped electrons from metal if, and only if, those packets had an energy level that could be absorbed by the atoms. of metal. The idea that light could be quantized was not new, years before this idea had been applied to thermal radiation by the German physicist Max Planck, which explained the phenomenon of black body issue.
In 1923, Louis De Broglie suggested that particles were also capable of behaving like waves. THE de Broglie's hypothesis, as it became known, suggested the existence of "particle waves", with this, it was expected that electrons, protons and other subatomic particles could present effects until then exclusively wavelike, such as refraction (change of wave velocity), diffraction (ability of waves to get around obstacles) etc.
De Broglie's hypothesis was confirmed in 1928 by the Davisson-Germer experiment, which consisted of promoting the diffraction of electrons. To do this, a cathode beam was directed at a nickel target that could be rotated, so as to change the angle at which the electron beam focused on the plane of nickel atoms. nonickel.
The results showed intensity peaks for particles that were reflected at certain angles, indicating the existence of a pattern of constructive and destructive interferences for the reflection of the electrons. The conclusion of the experiment was that electrons can be diffracted and produce interference, as did the electromagnetic waves.
The following figure illustrates the situation in which electrons are diffracted: according to distance traversed by each electron, a pattern of intensities was formed, just as happens for a wave diffracted by a crackpair.
See too: What are Bblack uracos?
Explanation of wave-particle duality
The explanation for the wave-particle duality emerged with the advance of quantum mechanics. Currently, it is known that all quantum systems are governed by a mechanism known as Heisenberg's Uncertainty Principle. According to this principle, particles are like a “field of matter”, since it is not possible to determine with absolute certainty the position of a quantum particle.
From the development of the Schroedinger's equation, we come to understand that all particles are completely characterized by a wave function, which nothing it is more than a mathematical expression that carries all the information that can be extracted from it. particle.
Before we observe a quantum system, its information is indeterminate, after observed, it is possible to locate and measure them, in this case, we say that its wave function has collapsed, presenting itself in one of its possible states. In other words, what determines whether a quantum entity is a wave or a particle is the act of observation, because it is possible that an experiment is carried out and a corpuscular behavior is observed and another experiment reveals an undulatory behavior - all thanks to the oddsgivesphysicsquantum.
By Rafael Hellerbrock
Physics teacher
