Wave-particle duality

In physics, wave-particle duality holds that light and matter can exhibit properties of both waves and of particles. This concept is a key part of quantum mechanics.

De Broglie

In 1924, de Broglie claimed that all matter has a wave-like nature; he related wavelength, λ, and momentum, p:

Related Topics:
1924 - De Broglie - Wavelength - Momentum

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:lambda = rac{h}{p}.

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This is a generalization of Einstein's equation above since the momentum of a photon is given by p = E / c

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where c is the speed of light in vacuum, and λ = c / ν.

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De Broglie's formula was confirmed three years later by Clinton Joseph Davisson and Lester Halbert Germer, by guiding a beam of electrons (which have rest mass) through a crystalline grid and observing the predicted interference patterns.

Related Topics:
Clinton Joseph Davisson - Lester Halbert Germer - Electron

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Similar experiments have since been conducted with neutrons and protons. Authors of similar recent experiments with atoms and molecules claim that these larger particles also act like waves. The most famous experiments are those of Estermann and Otto Stern in 1929, and the diffraction of fullerene C60 by researchers from the University of Vienna {{fn|1}} in 1999; in the later case, the wavelength of de Broglie is 2.5 pm whereas the diameter of the molecule is about 1 nm, i.e. about 400 times larger.

Related Topics:
Otto Stern - 1929 - Fullerene - University of Vienna - 1999 - Pm - Nm

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This is still a controversial subject because these experimenters have assumed arguments of wave-particle duality and have assumed the validity of deBroglie's equation in their argument.

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The Planck constant h is extremely small and that explains why we don't perceive a wave-like quality of everyday objects:

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their wavelengths are exceedingly small. The fact that matter can have very short wavelengths is exploited in electron microscopy.

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In quantum mechanics, the wave-particle duality is explained as follows: every system and particle is described by state functions which encode the probability distributions of all measurable variables. The position of the particle is one such variable. Before an observation is made the position of the particle is described in terms of probability waves which can interfere with each other.

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In quantum electrodynamics, Richard Feynman shows the wave-particle duality of photons and electrons is an illusion. In his view, photons and electrons obey rules that share some qualities of both particles and waves. They are neither particle nor wave, but some generalized object with no direct macroscopic analog.

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