n 1901, Max Planck used quanta to mean "quanta of matter and electricity",[5] gas, and heat.
[6] In
1905, in response to Planck's work and the experimental work of Lenard (who explained his results
by using the term quanta of electricity), Albert Einstein suggested that radiation existed in spatially
localized packets which he called "quanta of light" ("Lichtquanta").[7]
The concept of quantization of radiation was discovered in 1900 by Max Planck, who had been
trying to understand the emission of radiation from heated objects, known as black-body radiation.
By assuming that energy can be absorbed or released only in tiny, differential, discrete packets
(which he called "bundles", or "energy elements"),[8] Planck accounted for certain objects changing
colour when heated.[9] On December 14, 1900,
For other uses, see Quantum (disambiguation).
In physics, a quantum (plural: quanta) is the minimum amount of any physical entity (physical
property) involved in an interaction. The fundamental notion that a physical property may be
"quantized" is referred to as "the hypothesis of quantization".[1] This means that the magnitude of the
physical property can take on only discrete values consisting of integer multiples of one quantum.
For example, a photon is a single quantum of light (or of any other form of electromagnetic
radiation). Similarly, the energy of an electron bound within an atom is quantized and can exist only
in certain discrete values. (Indeed, atoms and matter in general are stable because electrons can
exist only at discrete energy levels within an atom.) Quantization is one of the foundations of the
much broader physics of quantum mechanics. Quantization of energy and its influence on how
energy and matter interact (quantum electrodynamics) is part of the fundamental framework for
understanding and describing nature.
Contents
1Etymology and discovery
2Beyond electromagnetic radiation
3See also
4References
5Further reading
Etymology and discovery[edit]
The word quantum comes from the Latin quantus, meaning "how great". "Quanta", short for "quanta
of electricity" (electrons), was used in a 1902 article on the photoelectric effect by Philipp Lenard,
who credited Hermann von Helmholtz for using the word in the area of electricity. However, the
word quantum in general was well known before 1900.[2] It was often used by physicians, such as in
the term quantum satis. Both Helmholtz and Julius von Mayer were physicians as well as physicists.
Helmholtz used quantum with reference to heat in his article[3] on Mayer's work, and the
word quantum can be found in the formulation of the first law of thermodynamics by Mayer in his
letter[4] dated July 24, 1841.
In 1901, Max Planck used quanta to mean "quanta of matter and electricity",[5] gas, and heat.[6] In
1905, in response to Planck's work and the experimental work of Lenard (who explained his results
by using the term quanta of electricity), Albert Einstein suggested that radiation existed in spatially
localized packets which he called "quanta of light" ("Lichtquanta").[7]
The concept of quantization of radiation was discovered in 1900 by Max Planck, who had been
trying to understand the emission of radiation from heated objects, known as black-body radiation.
By assuming that energy can be absorbed or released only in tiny, differential, discrete packets
(which he called "bundles", or "energy elements"),[8] Planck accounted for certain objects changing
colour when heated.[9] On December 14, 1900, Planck reported his findings to the German Physical
Society, and introduced the idea of quantization for the first time as a part of his research on black-
body radiation.[10] As a result of his experiments, Planck deduced the numerical value of h, known as
the Planck constant, and reported more precise values for the unit of electrical chargeand
the Avogadro–Loschmidt number, the number of real molecules in a mole, to the German Physical
Society. After his theory was validated, Planck was awarded the Nobel Prize in Physics for his
discovery in 1918.
Beyond electromagnetic radiation[edit]
While quantization was first discovered in electromagnetic radiation, it describes a fundamental
aspect of energy not just restricted to photons.[11] In the attempt to bring theory into agreement with
experiment, Max Planck postulated that electromagnetic energy is absorbed or emitted in discrete
packets, or quanta.[12]
See also[edit]
Elementary particle
Graviton
Introduction to quantum mechanics
Magnetic flux quantum
Photon
Photon polarization
Quantization (physics)
Quantum cellular automata
Quantum channel
Quantum coherence
Quantum chromodynamics
Quantum computer
Quantum cryptography
Quantum dot
Quantum electrodynamics
Quantum electronics
Quantum entanglement
Quantum Field Theory
Quantum immortality
Quantum lithography
Quantum Mechanics
Quantum number
Quantum Optics
Quantum sensor
Quantum state
Subatomic particle
Quantum teleportation
