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". The word quanta (singular quantum) was used even before 1900 to mean particles or amounts of different quantities, including electricity. Later, in 1905, Albert Einstein went further by suggesting that electromagnetic waves could only exist in these discrete wave-packets.[5] He called such a wave-packet the light quantum (German: das Lichtquant). The name photon derives from the Greek word for light, φῶς (transliterated phôs). Physical properties[edit] The cone shows possible values of wave 4-vector of a photon. A photon is massless,[Note 2] has no electric charge,[13] and is stable. Photons are emitted in many natural processes. Since p points in the direction of the photon's propagation, the magnitude of the momentum is
Complementarity (physics) In physics, complementarity is a fundamental principle of quantum mechanics, closely associated with the Copenhagen interpretation. It holds that objects governed by quantum mechanics, when measured, give results that depend inherently upon the type of measuring device used, and must necessarily be described in classical mechanical terms. Further, a full description of a particular type of phenomenon can only be achieved through measurements made in each of the various possible bases — which are thus complementary. The complementarity principle was formulated by Niels Bohr, the developer of the Bohr model of the atom, and a leading founder of quantum mechanics.[1] Bohr summarized the principle as follows: ...however far the [quantum physical] phenomena transcend the scope of classical physical explanation, the account of all evidence must be expressed in classical terms. For example, the particle and wave aspects of physical objects are such complementary phenomena. Physicists F.A.M. Dr.
On the origins of the Schrodinger equation (Phys.org) —One of the cornerstones of quantum physics is the Schrödinger equation, which describes what a system of quantum objects such as atoms and subatomic particles will do in the future based on its current state. The classical analogies are Newton's second law and Hamiltonian mechanics, which predict what a classical system will do in the future given its current configuration. Although the Schrödinger equation was published in 1926, the authors of a new study explain that the equation's origins are still not fully appreciated by many physicists. In a new paper published in PNAS, Wolfgang P. Schleich, et al., from institutions in Germany and the US, explain that physicists usually reach the Schrödinger equation using a mathematical recipe. Although much of the paper involves complex mathematical equations, the physicists describe the question of the Schrödinger equation's origins in a poetic way: Coauthor Marlan O. Explore further: Beam me up ...
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. Examples of thermal radiation include the visible light and infrared light emitted by an incandescent light bulb, the infrared radiation emitted by animals and detectable with an infrared camera, and the cosmic microwave background radiation. Thermal radiation is one of the fundamental mechanisms of heat transfer. Overview[edit] Surface effects[edit] Here,
Uncertainty principle where ħ is the reduced Planck constant. The original heuristic argument that such a limit should exist was given by Heisenberg, after whom it is sometimes named the Heisenberg principle. This ascribes the uncertainty in the measurable quantities to the jolt-like disturbance triggered by the act of observation. Though widely repeated in textbooks, this physical argument is now known to be fundamentally misleading.[4][5] While the act of measurement does lead to uncertainty, the loss of precision is less than that predicted by Heisenberg's argument; the formal mathematical result remains valid, however. Since the uncertainty principle is such a basic result in quantum mechanics, typical experiments in quantum mechanics routinely observe aspects of it. Introduction[edit] Click to see animation. The superposition of several plane waves to form a wave packet. As a principle, Heisenberg's uncertainty relationship must be something that is in accord with all experience. . with yields where
Double-slit experiment Physics experiment, showing light can be modelled by both waves and particles Photons or particles of matter (like an electron) produce a wave pattern when two slits are used Light from a green laser passing through two slits 0.4mm wide and 0.1mm apart The experiment belongs to a general class of "double path" experiments, in which a wave is split into two separate waves (the wave is typically made of many photons and better referred to as a wave front, not to be confused with the wave properties of the individual photon) that later combine into a single wave. Other atomic-scale entities, such as electrons, are found to exhibit the same behavior when fired towards a double slit.[6] Additionally, the detection of individual discrete impacts is observed to be inherently probabilistic, which is inexplicable using classical mechanics.[6] The experiment can be done with entities much larger than electrons and photons, although it becomes more difficult as size increases. Overview[edit]
Absolute zero Absolute zero is the lower limit of the thermodynamic temperature scale, a ficticious state at which the enthalpy and entropy of a cooled ideal gas reaches its minimum value, taken as 0. The theoretical temperature is determined by extrapolating the ideal gas law; by international agreement, absolute zero is taken as −273.15° on the Celsius scale (International System of Units),[1][2] which equates to −459.67° on the Fahrenheit scale (English/United States customary units).[3] The corresponding Kelvin and Rankine temperature scales set their zero points at absolute zero by definition. The laws of thermodynamics dictate that absolute zero cannot be reached using only thermodynamic means,[clarification needed] as the temperature of the substance being cooled approaches the temperature of the cooling agent asymptotically. A system at absolute zero still possesses quantum mechanical zero-point energy, the energy of its ground state. The kinetic energy of the ground state cannot be removed.
Quantum entanglement Quantum entanglement is a physical phenomenon that occurs when pairs or groups of particles are generated or interact in ways such that the quantum state of each particle cannot be described independently – instead, a quantum state may be given for the system as a whole. Such phenomena were the subject of a 1935 paper by Albert Einstein, Boris Podolsky and Nathan Rosen,[1] describing what came to be known as the EPR paradox, and several papers by Erwin Schrödinger shortly thereafter.[2][3] Einstein and others considered such behavior to be impossible, as it violated the local realist view of causality (Einstein referred to it as "spooky action at a distance"),[4] and argued that the accepted formulation of quantum mechanics must therefore be incomplete. History[edit] However, they did not coin the word entanglement, nor did they generalize the special properties of the state they considered. Concept[edit] Meaning of entanglement[edit] Apparent paradox[edit] The hidden variables theory[edit]