A CDE Definition
The inherent contradiction in the way energy behaves. At the turn of the 20th century, it was believed that light was electromagnetic waves and electrons were particles. By the 1930s, it was determined that light behaves as if it were made up of particles (photons) as well as waves, and electrons also behave like waves. This has driven scientists to drink and is one of the most puzzling phenomena in the universe. See quantum mechanics.
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 the 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 and quantum state.
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
1927 Born Interpretation of the
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