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Wave–particle duality

Wave–particle duality
Origin of theory[edit] The idea of duality originated in a debate over the nature of light and matter that dates back to the 17th century, when Christiaan Huygens and Isaac Newton proposed competing theories of light: light was thought either to consist of waves (Huygens) or of particles (Newton). Through the work of Max Planck, Albert Einstein, Louis de Broglie, Arthur Compton, Niels Bohr, and many others, current scientific theory holds that all particles also have a wave nature (and vice versa).[2] This phenomenon has been verified not only for elementary particles, but also for compound particles like atoms and even molecules. For macroscopic particles, because of their extremely short wavelengths, wave properties usually cannot be detected.[3] Brief history of wave and particle viewpoints[edit] Thomas Young's sketch of two-slit diffraction of waves, 1803 Particle impacts make visible the interference pattern of waves. A quantum particle is represented by a wave packet.

Related:  spacetimeMatter

Uncertainty principle Introduced first in 1927, by the German physicist Werner Heisenberg, it states that the more precisely the position of some particle is determined, the less precisely its momentum can be known, and vice versa.[1] The formal inequality relating the standard deviation of position σx and the standard deviation of momentum σp was derived by Earle Hesse Kennard[2] later that year and by Hermann Weyl[3] in 1928: (ħ is the reduced Planck constant, h / 2π). Since the uncertainty principle is such a basic result in quantum mechanics, typical experiments in quantum mechanics routinely observe aspects of it. Ionization Ionization (or ionisation, see American and British English spelling differences) is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons. Ionization, often, results from the interaction of an atom or a molecule with an ionizing particle, including charged particles with sufficient energies and energetic photons. A rare case of ionization in the absence of an external particle is the internal conversion process, through which an excited nucleolus transfers its energy to one of the inner-shell electrons and ejects it with high kinetic energy. The ionization process is of particular interest in fundamental science.

Photon Nomenclature[edit] In 1900, Max Planck was working on black-body radiation and suggested that the energy in electromagnetic waves could only be released in "packets" of energy. In his 1901 article [4] in Annalen der Physik he called these packets "energy elements". Quantum tunnelling Quantum tunnelling or tunneling (see spelling differences) refers to the quantum mechanical phenomenon where a particle tunnels through a barrier that it classically could not surmount. This plays an essential role in several physical phenomena, such as the nuclear fusion that occurs in main sequence stars like the Sun.[1] It has important applications to modern devices such as the tunnel diode,[2] quantum computing, and the scanning tunnelling microscope. The effect was predicted in the early 20th century and its acceptance as a general physical phenomenon came mid-century.[3] Tunnelling is often explained using the Heisenberg uncertainty principle and the wave–particle duality of matter. Pure quantum mechanical concepts are central to the phenomenon, so quantum tunnelling is one of the novel implications of quantum mechanics. History[edit]

Thermal radiation This diagram shows how the peak wavelength and total radiated amount vary with temperature according to Wien's displacement law. Although this plot shows relatively high temperatures, the same relationships hold true for any temperature down to absolute zero. Visible light is between 380 and 750 nm. Thermal radiation in visible light can be seen on this hot metalwork. Its emission in the infrared is invisible to the human eye and the camera the image was taken with, but an infrared camera could show it (See Thermography). Thermal radiation is electromagnetic radiation generated by the thermal motion of charged particles in matter. Introduction to quantum mechanics This article is a non-technical introduction to the subject. For the main encyclopedia article, see Quantum mechanics. In this sense, the word quantum means the minimum amount of any physical entity involved in an interaction. Certain characteristics of matter can take only discrete values. Some aspects of quantum mechanics can seem counterintuitive or even paradoxical, because they describe behaviour quite different from that seen at larger length scales.

Brownian motion This is a simulation of the Brownian motion of a big particle (dust particle) that collides with a large set of smaller particles (molecules of a gas) which move with different velocities in different random directions. This is a simulation of the Brownian motion of 5 particles (yellow) that collide with a large set of 800 particles. The yellow particles leave 5 blue trails of random motion and one of them has a red velocity vector. Three different views of Brownian motion, with 32 steps, 256 steps, and 2048 steps denoted by progressively lighter colors A single realisation of three-dimensional Brownian motion for times 0 ≤ t ≤ 2

Phase space Phase space of a dynamic system with focal instability, showing one phase space trajectory A plot of position and momentum variables as a function of time is sometimes called a phase plot or a phase diagram. Phase diagram, however, is more usually reserved in the physical sciences for a diagram showing the various regions of stability of the thermodynamic phases of a chemical system, which consists of pressure, temperature, and composition. In classical mechanics, any choice of generalized coordinates q i for the position (i.e. coordinates on configuration space) defines conjugate generalized momenta pi which together define co-ordinates on phase space. More abstractly, in classical mechanics phase space is the cotangent space of configuration space, and in this interpretation the procedure above expresses that a choice of local coordinates on configuration space induces a choice of natural local Darboux coordinates for the standard symplectic structure on a cotangent space.