# wave mechanics

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## wave mechanics:

see quantum theory**quantum theory,**

modern physical theory concerned with the emission and absorption of energy by matter and with the motion of material particles; the quantum theory and the theory of relativity together form the theoretical basis of modern physics.

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## Wave mechanics

The modern theory of matter holding that elementary particles (such as electrons, protons, and neutrons) have wavelike properties. In 1924 L. de Broglie postulated that the wave-particle duality which had been demonstrated for electromagnetic radiation also was a property of the elementary particles making up the atoms and molecules forming ordinary matter. In particular, de Broglie postulated that a particle has an associated wavelength obeying the same relation as was found to hold for photons, namely: the wavelength equals Planck's constant divided by the particle's momentum (as customarily defined in elementary mechanics). This hypothesis was verified in 1927 in an experiment in which a beam of electrons having known momentum is diffracted by a crystal into special directions. Such diffraction seems understandable only on the hypothesis that the electrons are waves. Furthermore, the wavelength of the electrons in the incident beam, computed via the same formula as was used to derive x-ray wavelengths in x-ray diffraction experiments, agreed precisely with the de Broglie relation. *See* Electron diffraction, X-ray diffraction

Subsequent experiments have confirmed that not merely electrons but material particles in general, such as neutrons and neutral sodium atoms, manifest the wave-particle duality and obey the de Broglie relation. The de Broglie relation and the qualitative wave-particle duality concept have been incorporated into the highly successful modern theory of quantum mechanics. *See* Atom optics, De Broglie wavelength, Interference of waves, Quantum mechanics