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The other exemplar that led to quantum mechanics was the study of [http://en.wikipedia.org/wiki/Electromagnetic_wave electromagnetic waves] such as [[light]]. When it was found in 1900 by Max Planck that the energy of waves could be described as consisting of small packets or quanta, [[Albert Einstein]] exploited this idea to show that an electromagnetic wave such as light could be described by a particle called the [[photon]] with a discrete energy dependent on its frequency. This led to a theory of unity between subatomic particles and electromagnetic waves called wave–particle duality in which particles and waves were neither one nor the other, but had certain properties of both. While quantum mechanics describes the world of the very small, it also is needed to explain certain “macroscopic quantum systems” such as superconductors and superfluids.[11]

The other exemplar that led to quantum mechanics was the study of [http://en.wikipedia.org/wiki/Electromagnetic_wave electromagnetic waves] such as [[light]]. When it was found in 1900 by Max Planck that the energy of waves could be described as consisting of small packets or quanta, [[Albert Einstein]] exploited this idea to show that an electromagnetic wave such as light could be described by a particle called the [[photon]] with a discrete energy dependent on its frequency. This led to a theory of unity between subatomic particles and electromagnetic waves called wave–particle duality in which particles and waves were neither one nor the other, but had certain properties of both. While quantum mechanics describes the world of the very small, it also is needed to explain certain “macroscopic quantum systems” such as superconductors and superfluids.[11]

Broadly speaking, quantum mechanics incorporates four classes of [[phenomena]] that classical physics cannot account for: (I) the [http://en.wikipedia.org/wiki/Quantization_(physics) quantization] (discretization) of certain physical quantities, (II) [http://en.wikipedia.org/wiki/Wave-particle_duality wave-particle duality], (III) [http://en.wikipedia.org/wiki/Uncertainty_principle the uncertainty principle], and (IV) [http://en.wikipedia.org/wiki/Quantum_entanglement quantum entanglement]. Each of these phenomena is described in detail in the article found at [http://en.wikipedia.org/wiki/Quantum_mechanics this link].

Broadly speaking, quantum mechanics incorporates four classes of [[phenomena]] that classical physics cannot account for: (I) the [http://en.wikipedia.org/wiki/Quantization_(physics) quantization] (discretization) of certain physical quantities, (II) [http://en.wikipedia.org/wiki/Wave-particle_duality wave-particle duality], (III) [http://en.wikipedia.org/wiki/Uncertainty_principle the uncertainty principle], and (IV) [http://en.wikipedia.org/wiki/Quantum_entanglement quantum entanglement]. Each of these phenomena is described in detail in the article found at [http://en.wikipedia.org/wiki/Quantum_mechanics this link].

==References==

==References==

The following titles, all by working physicists, attempt to [[communicate]] '''quantum theory''' to lay people, using a minimum of technical apparatus.

The following titles, all by working physicists, attempt to [[communicate]] '''quantum theory''' to lay people, using a minimum of technical apparatus.