A 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, such as 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 also: Bosons, Fermions, Leptons – Standard Model of Particle Physics
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Difference between wave and particle
Before we talk about wave-particle duality, it is important to understand the characteristics of each of these aspects.
To the particles:
- occupy a position in space,
- are endowed with mass,
- have definite shape,
- are well localized, that is, their position can be easily determined.
already the waves:
- are disturbances in space,
- have no definite position,
- have no mass,
- are phenomena that transport energy,
- are subject to the phenomena of reflection, refraction, diffraction, interference, etc.
Although they are 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 the form of a wave or in the form of a particle, is related to the way it is observed.
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wave-particle duality
The wave-particle duality came to be questioned when Heinrich Hertz’s experimental results concerning the photoelectric effect came into question. direct contradiction with what was expected for the behavior of lightaccording to the electromagnetic theory of James Clerk Maxwell.
According to the prevailing theory at the time, any frequency of light should be able to eject electrons of a metallic foil, however, Hertz’s results showed that it was only from certain frequencies that such emission was detected.
A 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 knocked electrons out of the metal if, and only if, these packages had an energy level that could be absorbed by the metal atoms. 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 Planckwhich explains the phenomenon of black body emission.
According to modern knowledge of Physics, matter has wave behavior.
In 1923, Louis De Broglie suggested that particles were also capable of behaving like waves. A de Broglie hypothesisas it became known, suggested the existence of “particle waves”therefore, it was expected that electrons, protons and other subatomic particles could present effects that were until then exclusively wave-like, such as refraction (change in the speed of waves), diffraction (ability of waves to circumvent obstacles) etc.
De Broglie’s hypothesis was confirmed in 1928 by the Davisson-Germer experimentwhich was to promote the diffraction of electrons. For this to be done, a cathode beam was directed at a nickel target that could be rotated, so as to change the angle at which the electron beam fell on the plane of nickel atoms. nnickel.
The results showed intensity peaks for particles that were reflected at certain angles, indicating the existence of a pattern of constructive and destructive interference for the reflection of electrons. The conclusion of the experiment was that electrons can be diffracted and produce interferenceas did the electromagnetic waves.
The following figure illustrates the situation in which electrons are diffracted: according to the distance traveled by each electron, a pattern of intensities was formed, just as it happens for a wave diffracted by a slit pair.
See also: What are black holes?
Explanation of wave-particle duality
The explanation for the wave-particle duality emerged with the advance of quantum mechanics. It is now known that all quantum systems are governed by a mechanism known as the Heisenberg uncertainty principle. According to this principle, particles are like a “matter field”, since it is not possible to determine with absolute certainty the position of a quantum particle.
From the development of Schroedinger equationwe come to understand that all particles are completely characterized by a wave function, which is nothing more than a mathematical expression that carries with it all the information that can be extracted from that particle.
Before we observe a quantum system, its information is indeterminate, after being observed, it is possible to locate and measure it, in this case, we say that its wave function 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 itself. act of observationbecause it is possible that an experiment is carried out and a corpuscular behavior is observed and another experiment reveals a wave behavior – all thanks to the probabilities from the physical quantum.
By Rafael Helerbrock
Physics teacher