# Quantum-mechanics definitions

Quantum theory, especially the quantum theory of the structure and behavior of atoms and molecules.

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A physical theory that describes the motion of objects by the principles of quantum theory.

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A fundamental theory of matter and energy that explains facts that previous physical theories were unable to account for, in particular the fact that energy is absorbed and released in small, discrete quantities (quanta), and that all matter displays both wavelike and particlelike properties, especially when viewed at atomic and subatomic scales. Quantum mechanics suggests that the behavior of matter and energy is inherently probabilistic and that the effect of the observer on the physical system being observed must be understood as a part of that system.

The branch of physics developed in the first part of the 20th century that was highly successful in explaining the behavior of atoms, molecules and nuclei. Developed between 1900 and 1930 and combined with Einstein's general and special theory of relativity, it revolutionized the field of physics. The new concepts, which were the particle properties of radiation, the wave properties of matter, quantization of physical properties and the idea that one can no longer know exactly where a single particle such as an electron is at any one instance were necessary to explain all of the new experimental evidence that was available at the time. For example, quantum mechanics explains the behavior of semiconductors which are used to make the myriad devices we use every day. See wave-particle duality, quantum state and quantum computing.Following are the important contributors to the foundation of quantum mechanics and the principles they uncovered.

**Year Researcher Contribution**1901 Planck Blackbody radiation 1905 Einstein Photoelectric effect 1913 Bohr Spectra theory 1922 Compton Photon scattering 1924 Pauli Exclusion principle 1925 de Broglie Matter waves 1926 Schroedinger Wave equation 1927 Heisenberg Uncertainty principle 1927 Davison & Wave properties of Germer electrons 1927 Born Interpretation of the wavefunction.(physics) The branch of physics which studies matter and energy at the level of atoms and other elementary particles, and substitutes probabilistic mechanisms in place of classical Newtonian ones.

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