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 relativityrelativity,
physical theory, introduced by Albert Einstein, that discards the concept of absolute motion and instead treats only relative motion between two systems or frames of reference.
..... Click the link for more information. together form the theoretical basis of modern physics. Just as the theory of relativity assumes importance in the special situation where very large speeds are involved, so the quantum theory is necessary for the special situation where very small quantities are involved, i.e., on the scale of moleculesmolecule
[New Lat.,=little mass], smallest particle of a compound that has all the chemical properties of that compound. A single atom is usually not referred to as a molecule, and ionic compounds such as common salt are not made up of molecules.
..... Click the link for more information. , atomsatom
[Gr.,=uncuttable (indivisible)], basic unit of matter; more properly, the smallest unit of a chemical element having the properties of that element. Structure of the Atom
..... Click the link for more information. , and elementary particleselementary particles,
the most basic physical constituents of the universe. Basic Constituents of Matter

Molecules are built up from the atom, which is the basic unit of any chemical element. The atom in turn is made from the proton, neutron, and electron.
..... Click the link for more information. . Aspects of the quantum theory have provoked vigorous philosophical debates concerning, for example, the uncertainty principle and the statistical nature of all the predictions of the theory.

Relationship of Energy and Matter

According to the older theories of classical physics, energy is treated solely as a continuous phenomenon, while matter is assumed to occupy a very specific region of space and to move in a continuous manner. According to the quantum theory, energy is held to be emitted and absorbed in tiny, discrete amounts. An individual bundle or packet of energy, called a quantum (pl. quanta), thus behaves in some situations much like particles of matter; particles are found to exhibit certain wavelike properties when in motion and are no longer viewed as localized in a given region but rather as spread out to some degree.

For example, the light or other radiation given off or absorbed by an atom has only certain frequencies (or wavelengths), as can be seen from the line spectrumspectrum,
arrangement or display of light or other form of radiation separated according to wavelength, frequency, energy, or some other property. Beams of charged particles can be separated into a spectrum according to mass in a mass spectrometer (see mass spectrograph).
..... Click the link for more information. associated with the chemical element represented by that atom. The quantum theory shows that those frequencies correspond to definite energies of the light quanta, or photonsphoton
, the particle composing light and other forms of electromagnetic radiation, sometimes called light quantum. The photon has no charge and no mass. About the beginning of the 20th cent.
..... Click the link for more information. , and result from the fact that the electrons of the atom can have only certain allowed energy values, or levels; when an electron changes from one allowed level to another, a quantum of energy is emitted or absorbed whose frequency is directly proportional to the energy difference between the two levels.

Dual Nature of Waves and Particles

The restriction of the energy levels of the electrons is explained in terms of the wavelike properties of their motions: electrons occupy only those orbits for which their associated wave is a standing wave (i.e., the circumference of the orbit is exactly equal to a whole number of wavelengths) and thus can have only those energies that correspond to such orbits. Moreover, the electrons are no longer thought of as being at a particular point in the orbit but rather as being spread out over the entire orbit. Just as the results of relativity approximate those of Newtonian physics when ordinary speeds are involved, the results of the quantum theory agree with those of classical physics when very large "quantum numbers" are involved, i.e., on the ordinary large scale of events; this agreement in the classical limit is required by the correspondence principlecorrespondence principle,
physical principle, enunciated by Niels Bohr in 1923, according to which the predictions of the quantum theory must correspond to the predictions of the classical theories of physics when the quantum theory is used to describe the behavior of systems
..... Click the link for more information. of Niels BohrBohr, Niels Henrik David
, 1885–1962, Danish physicist, one of the foremost scientists of modern physics. He studied at the Univ. of Copenhagen (Ph.D. 1911) and carried on research on the structure of the atom at Cambridge under Sir James J.
..... Click the link for more information. . The quantum theory thus proposes a dual nature for both waves and particles, one aspect predominating in some situations, the other predominating in other situations.

Evolution of Quantum Theory

Early Developments

While the theory of relativity was largely the work of one man, Albert EinsteinEinstein, Albert
, 1879–1955, American theoretical physicist, known for the formulation of the relativity theory, b. Ulm, Germany. He is recognized as one of the greatest physicists of all time.
..... Click the link for more information. , the quantum theory was developed principally over a period of thirty years through the efforts of many scientists. The first contribution was the explanation of blackbodyblackbody,
in physics, an ideal black substance that absorbs all and reflects none of the radiant energy falling on it. Lampblack, or powdered carbon, which reflects less than 2% of the radiation falling on it, crudely approximates an ideal blackbody; a material consisting of a
..... Click the link for more information. radiation in 1900 by Max PlanckPlanck, Max
, 1858–1947, German physicist. Seeking to explain the experimental spectrum (distribution of electromagnetic energy according to wavelength) of blackbody radiation, he introduced the hypothesis (1900) that oscillating atoms absorb and emit energy only in
..... Click the link for more information. , who proposed that the energies of any harmonic oscillator (see harmonic motionharmonic motion,
regular vibration in which the acceleration of the vibrating object is directly proportional to the displacement of the object from its equilibrium position but oppositely directed.
..... Click the link for more information. ), such as the atoms of a blackbody radiator, are restricted to certain values, each of which is an integral (whole number) multiple of a basic, minimum value. The energy E of this basic quantum is directly proportional to the frequency ν of the oscillator, or E=hν, where h is a constant, now called Planck's constant, having the value 6.62607×10⁻³⁴ joule-second. In 1905, Einstein proposed that the radiation itself is also quantized according to this same formula, and he used the new theory to explain the photoelectric effectphotoelectric effect,
emission of electrons by substances, especially metals, when light falls on their surfaces. The effect was discovered by H. R. Hertz in 1887. The failure of the classical theory of electromagnetic radiation to explain it helped lead to the development of
..... Click the link for more information. . Following the discovery of the nuclear atom by RutherfordRutherford, Ernest Rutherford, 1st Baron,
1871–1937, British physicist, b. New Zealand. Rutherford left New Zealand in 1895, having earned three degrees from the Univ.
..... Click the link for more information. (1911), Bohr used the quantum theory in 1913 to explain both atomic structure and atomic spectra, showing the connection between the electrons' energy levels and the frequencies of light given off and absorbed.

Quantum Mechanics and Later Developments

Quantum mechanics, the final mathematical formulation of the quantum theory, was developed during the 1920s. In 1924, Louis de BroglieBroglie, Louis Victor, duc de,
1892–1987, French physicist. In 1928 he became professor in the faculty of sciences, Univ. of Paris. It was known from the earlier quantum theory that light waves sometimes exhibited a particlelike behavior.
..... Click the link for more information. proposed that not only do light waves sometimes exhibit particlelike properties, as in the photoelectric effect and atomic spectra, but particles may also exhibit wavelike properties. This hypothesis was confirmed experimentally in 1927 by C. J. DavissonDavisson, Clinton Joseph
, 1881–1958, American physicist, b. Bloomington, Ill. He joined the engineering department of the Bell Telephone Laboratories in 1917. Davisson worked on thermionics, magnetism, and electron diffraction. His demonstrations with L. H.
..... Click the link for more information. and L. H. Germer, who observed diffractiondiffraction,
bending of waves around the edge of an obstacle. When light strikes an opaque body, for instance, a shadow forms on the side of the body that is shielded from the light source.
..... Click the link for more information. of a beam of electrons analogous to the diffraction of a beam of light. Two different formulations of quantum mechanics were presented following de Broglie's suggestion. The wave mechanics of Erwin SchrödingerSchrödinger, Erwin
, 1887–1961, Austrian theoretical physicist. He was educated at Vienna, taught at Breslau and Zürich, and was professor at the Univ. of Berlin (1927–33), fellow of Magdalen College, Oxford (1933–36), and professor at the Univ.
..... Click the link for more information. (1926) involves the use of a mathematical entity, the wave function, which is related to the probability of finding a particle at a given point in space. The matrix mechanics of Werner Heisenberg (1925) makes no mention of wave functions or similar concepts but was shown to be mathematically equivalent to Schrödinger's theory.

Quantum mechanics was combined with the theory of relativity in the formulation of P. A. M. DiracDirac, Paul Adrien Maurice
, 1902–84, English physicist. He was educated at the Univ. of Bristol and St. John's College, Cambridge, and became professor of mathematics at Cambridge in 1932.
..... Click the link for more information. (1928), which, in addition, predicted the existence of antiparticlesantiparticle,
elementary particle corresponding to an ordinary particle such as the proton, neutron, or electron, but having the opposite electrical charge and magnetic moment.
..... Click the link for more information. . A particularly important discovery of the quantum theory is the uncertainty principleuncertainty principle,
physical principle, enunciated by Werner Heisenberg in 1927, that places an absolute, theoretical limit on the combined accuracy of certain pairs of simultaneous, related measurements.
..... Click the link for more information. , enunciated by HeisenbergHeisenberg, Werner
, 1901–76, German physicist. One of the founders of the quantum theory, he is best known for his uncertainty principle, or indeterminacy principle, which states that it is impossible to determine with arbitrarily high accuracy both the position and
..... Click the link for more information. in 1927, which places an absolute theoretical limit on the accuracy of certain measurements; as a result, the assumption by earlier scientists that the physical state of a system could be measured exactly and used to predict future states had to be abandoned. Other developments of the theory include quantum statistics, presented in one form by Einstein and S. N. Bose (the Bose-Einstein statisticsBose-Einstein statistics,
class of statistics that applies to elementary particles called bosons, which include the photon, pion, and the W and Z particles. Bosons have integral values of the quantum mechanical property called spin and are "gregarious" in the sense that an
..... Click the link for more information. ) and in another by Dirac and Enrico FermiFermi, Enrico
, 1901–54, American physicist, b. Italy. He studied at Pisa, Göttingen, and Leiden, and taught physics at the universities of Florence and Rome. He contributed to the early theory of beta decay and the neutrino and to quantum statistics.
..... Click the link for more information. (the Fermi-Dirac statisticsFermi-Dirac statistics,
class of statistics that applies to particles called fermions. Fermions have half-integral values of the quantum mechanical property called spin and are "antisocial" in the sense that two fermions cannot exist in the same state.
..... Click the link for more information. ); quantum electrodynamicsquantum electrodynamics
(QED), quantum field theory that describes the properties of electromagnetic radiation and its interaction with electrically charged matter in the framework of quantum theory.
..... Click the link for more information. , concerned with interactions between charged particles and electromagnetic fieldsfield,
in physics, region throughout which a force may be exerted; examples are the gravitational, electric, and magnetic fields that surround, respectively, masses, electric charges, and magnets. The field concept was developed by M.
..... Click the link for more information. ; its generalization, quantum field theoryquantum field theory,
study of the quantum mechanical interaction of elementary particles and fields. Quantum field theory applied to the understanding of electromagnetism is called quantum electrodynamics (QED), and it has proved spectacularly successful in describing the
..... Click the link for more information. ; and quantum electronics.

Bibliography

See W. Heisenberg, The Physical Principles of the Quantum Theory (1930) and Physics and Philosophy (1958); G. Gamow, Thirty Years that Shook Physics (1966); J. Gribbin, In Search of Schrödinger's Cat (1984).

quantum theory

The theory put forward by the German physicist Max Planck in 1900. Classical physics regarded all changes in the physical properties of a system to be continuous. By departing from this viewpoint and allowing physical quantities such as energy, angular momentum, and action to change only by discrete amounts, quantum theory was born. It grew out of Planck's attempts to explain the form of the curves of intensity against wavelength for a black-body radiator. By assuming that energy could only be emitted and absorbed in discrete amounts, called quanta, he was successful in describing the shape of the curves. Other early applications of quantum theory were Einstein's explanation of the photoelectric effect and Bohr's theory of the atom (see hydrogen spectrum; energy level). The more precise mathematical theory that developed in the 1920s from quantum theory is called quantum mechanics. Relativistic quantum mechanics resulted from the extension of quantum mechanics to include the special theory of relativity.

quantum theory

[′kwän·təm ‚thē·ə·rē] (physics) quantum mechanics

quantum theory

a theory concerning the behaviour of physical systems based on Planck's idea that they can only possess certain properties, such as energy and angular momentum, in discrete amounts (quanta). The theory later developed in several equivalent mathematical forms based on De Broglie's theory (see wave mechanics) and on the Heisenberg uncertainty principle

quantum theory

theory

[the´ah-re, thēr´e] 1. the doctrine or the principles underlying an art as distinguished from the practice of that particular art.2. a formulated hypothesis or, loosely speaking, any hypothesis or opinion not based upon actual knowledge.3. a provisional statement or set of explanatory propositions that purports to account for or characterize some phenomenon. The concepts and provisions set forth in a theory are more specific and concrete than those of a conceptual model. Hence a theory is derived from a conceptual model to fully describe, explain, and predict phenomena within the domain of the model.attribution theory a theory developed in an attempt to understand why an event occurred so that later events can be predicted and controlled.care-based theory a type of ethical theory of health care based on the two central constructive ideas of mutual interdependence and emotional response. The ethics of care is a rejection of impartial, principle-driven, dispassionate reasoning and judgment that has often dominated the models and paradigms of bioethics. Its origins are developmental psychology, moral theory, and feminist writings. Its moral concern is with needs and corresponding responsibility as they arise within a relationship. Moral response is individualized and is guided by the private norms of friendship, love, and care rather than by abstract rights and principles.cell theory all organic matter consists of cells, and cell activity is the essential process of life.clonal-selection theory of immunity immunologic specificity is preformed during embryonic life and mediated through cell clones.Cohnheim's theory tumors develop from embryonic rests that do not participate in the formation of normal surrounding tissue.community-based theory any ethical theory of health care according to which everything fundamental in ethics derives from communal values, the common good, social goals, traditional practices, and cooperative virtues. Commitment is to the general welfare, to common purposes, and to education of community members. Beliefs and principles, shared goals, and obligations are seen as products of the communal life. Conventions, traditions, and social solidarity play a prominent role in this type of theory. Called also communitarianism.consequence-based theory teleological theory.continuity theory a theory of motor development that postulates that motor changes occur in a linear fashion during an individual's life and that each change is dependent on the development of the prior period.deontological theory a type of ethical theory that maintains that some features of actions other than or in addition to consequences make the actions right or wrong. A major postulate is that we may not use or mistreat other people as a means to our own happiness or to that of others. Deontological theories guide action with a set of moral principles or moral rules, but it is the actions themselves and their moral properties that are fundamental. This theory is sometimes called the Kantian theory because the work of Immanuel Kant (1724–1804) has a deep effect on its formulations.discontinuity theory each stage of motor development has a new and unique feature that is added to distinguish it from the previous stage.family systems theory a view of the family as a dynamic, interactive unit that undergoes continual evolvement in structure and function. There are subsystems that are discrete units (such as mother-father, sister-brother, and mother-child) and there is a suprasystem (the community). The main functions of the family are considered to be support, regulation, nurturance, and socialization; specific aspects of the functions change as the subsystems interact with the suprasystem.feminist theory a type of ethical theory whose core assumptions are that women's experiences have not been taken as seriously as men's experiences and that there is subordination of women, which must end. A central theme is that women's reality is a social construction and not a biological determination. See also praxis" >feminist praxis.gate theory (gate-control theory) neural impulses generated by noxious painful stimuli and transmitted to the spinal cord by small-diameter C-fibers and A-delta fibers are blocked at their synapses in the dorsal horn by the simultaneous stimulation of large-diameter myelinated A-fibers, thus inhibiting pain by preventing pain impulses from reaching higher levels of the central nervous system.

The gate-control theory of pain. From Linton et al., 2000.general systems theory a theory of organization proposed by Ludwig von Bertalanffy in the 1950s as a means by which various disciplines could communicate with one another and duplication of efforts among scientists could be avoided. The theory sought universally applicable principles and laws that would hold true regardless of the kind of system under study, the nature of its components, or the interrelationships among its components. Since the introduction of the general systems theory, theoretical models, principles, and laws have been developed that are of great value to scientists in all fields, including those of medicine, nursing, and other health-related professions.germ theory 1. all organisms are developed from a cell.2. infectious diseases are of microbial origin.theory of human becoming a theory of nursing formulated by Rosemarie Rizzo parse. Principles of Martha Rogers' science of unitary human beings are synthesized with major tenets and concepts from existential phenomenological thought to create a conceptual system and theory. Major areas of focus, rooted in the human sciences, describe the unitary human being interrelating with the universe in co-creating health. Essential concepts include the human-universe-health interrelationship, the co-creating of health, and the freely choosing of meaning in becoming. Humans are unitary beings mutually co-creating rhythmical patterns of relating in open interchange with the universe. The human being is a unity of the subject-world relationship, participating with the world in co-creation of self.

Health, in this theory, is a continuously changing process that humans participate in co-creating. Health is human becoming. It is not the opposite of disease, nor is it a state that exists. Disease is viewed as a pattern of the human being's interrelationship with the world.
Nursing is both science and art. The science is nursing's abstract body of knowledge lived through the art in service to people. Three principles of this theory comprise the abstract knowledge base used to guide nursing research and practice. The principles of structuring meaning multidimensionally, co-creating rhythmical patterns of relating, and co-transcending with the possibles provide the underpinnings for practice and research.
There is a particular nursing practice methodology, the only one that evolves directly from a nursing theory. Parse's practice methodology specifies that the nurse be truly present with the person and family illuminating meaning, synchronizing rhythms, and mobilizing transcendence. Persons choose their own patterns of health, reflective of their values. The nurse is there with the person and family as they uncover meanings and make decisions about their life situations. True presence is an unconditional love grounded in the belief that individuals know the way.
Parse has also constructed a research methodology congruent with her theory and unique to nursing. Her research methodology offers the researcher the opportunity to study universal lived experiences from the perspective of the people living the experiences. The purpose of her basic research method is to uncover the meaning of lived experiences to enhance the knowledge base of nursing. Parse has contributed to nursing science a theory with congruent practice and research methodologies.theory of human caring a nursing theory formulated by Jean watson, derived from the values and assumptions of metaphysical, phenomenological-existential, and spiritual conceptual orientations. The primary concepts of the theory, transpersonal human caring and caring transactions, are multidimensional giving and receiving responses between a nurse and another person. Transpersonal human caring implies a special kind of relationship where both the nurse and the other have a high regard for the whole person in a process of being and becoming. Caring transactions provide a coming together in a lived moment, an actual caring occasion that involves choice and action by both the nurse and another.

Person (other) is defined as an experiencing and perceiving “being in the world,” possessing three spheres; mind, body, and soul. Person is also defined as a living growing gestalt with a unique phenomenal field of subjective reality.
The environment includes an objective physical or material world and a spiritual world. Watson defines the world as including all forces in the universe as well as a person's immediate environment. Critical to this definition is the concept of transcendence of the physical world that is bound in time and space, making contact with the emotional and spiritual world by the mind and soul.
Health is more than the absence of disease. Health is unity and harmony within the mind, body, and soul and is related to the congruence between the self as perceived and the self as experienced.
Nursing is defined as a human science and an activity of art, centered on persons and human health-illness experiences. The goal of nursing is to help persons gain a higher level of harmony within the mind, body and soul. Nursing practice is founded on the human-to-human caring process and a commitment to caring as a moral ideal. The activities of nursing are guided by Watson's ten carative factors, which offer a descriptive topology of interventions. The nursing process is incorporated in these carative factors as “creative problem-solving caring process,” a broad approach to nursing that seeks connections and relations rather than separations.information theory a mathematical theory dealing with messages or signals, the distortion produced by statistical noise, and methods of coding that reduce distortion to the irreducible minimum.information processing theory a theory of learning that focuses on internal, cognitive processes in which the learner is viewed as a seeker and processor of information.Kantian theory deontological theory.Lamarck's theory the theory that acquired characteristics may be inherited.Metchnikoff theory the theory that harmful elements in the body are attacked by phagocytes, causing inflammation; see also metchnikoff theory" >metchnikoff theory.middle range theory a testable theory that contains a limited number of variables, and is limited in scope as well, yet is of sufficient generality to be useful with a variety of clinical research questions.nursing theory 1. a framework designed to organize knowledge and explain phenomena in nursing, at a more concrete and specific level than a conceptual model or a metaparadigm.2. The study and development of theoretical frameworks in nursing.obligation-based theory deontological theory.quantum theory radiation and absorption of energy occur in quantities (quanta) that vary in size with the frequency of the radiation.recapitulation theory ontogeny recapitulates phylogeny; see also recapitulation theory.rights-based theory a type of ethical theory under which the language of rights provides the basic terminology for ethical and political theory; it maintains that a democratic society must protect individuals and allow all to pursue personal goals. The idea of primacy of rights has been strongly disputed by, for example, utilitarians and Marxists. Individual interests often conflict with communal or institutional interests, as has been seen in efforts to reform the health care system. A prominent rights-based theory is what is known as liberal individualism.teleological theory a type of ethical theory that takes judgments of the value of the consequences of action as basic. Utilitarianism is the most prominent consequence-based theory; it accepts one and only one basic principle of ethics, the principle of utility, which asserts that we ought always to produce the maximal balance of positive value over negative consequences (or the least possible negative consequence, if only undesirable results can be achieved).Young-Helmholtz theory the theory that color vision depends on three sets of retinal receptors, corresponding to the colors of red, green, and violet.

quan·tum the·o·ry

that energy can be emitted, transmitted, and absorbed only in discrete quantities (quanta), so that atoms and subatomic particles can exist only in certain energy states. Synonym(s): Planck theory

quan·tum the·o·ry

(kwahn'tŭm thē'ŏr-ē) That energy can be emitted, transmitted, and absorbed only in discrete quantities (quanta), so that atoms and subatomic particles can exist only in certain energy states.
Synonym(s): Planck theory.

Planck,

Max, German physicist and Nobel laureate, 1858-1947. Planck constant - a natural constant occurring in many physical formulas.Planck theory - that energy can be emitted, transmitted, and absorbed only in discrete quantities. Synonym(s): quantum theory

quantum theory

quantum theory

quantum theory

quan′tum the`ory

quantum theory

quantum theory

quantum theory

quantum theory,

Relationship of Energy and Matter

Dual Nature of Waves and Particles

Evolution of Quantum Theory

Early Developments

Quantum Mechanics and Later Developments

Bibliography

quantum theory

quantum theory

quantum theory

quantum theory

theory

quan·tum the·o·ry

quan·tum the·o·ry

Planck,

quan·tum the·o·ry

quantum theory

Words related to quantum theory

noun (physics) a physical theory that certain properties occur only in discrete amounts (quanta)

Related Words