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Topic: Coherence (physics)


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In the News (Wed 24 Apr 19)

  
  Coherence (physics) - Wikipedia, the free encyclopedia
Coherence is the property of wave-like states that enables them to exhibit interference.
The property of coherence is the basis for commercial applications such as holography, the Sagnac gyroscope, radio antenna arrays, optical coherence tomography and telescope interferometers (astronomical optical interferometers and radio telescopes).
In optics, temporal coherence is measured in an interferometer such as the Michelson interferometer or Mach-Zehnder interferometer.
en.wikipedia.org /wiki/Coherence_(physics)   (2237 words)

  
 Coherence - Wikipedia, the free encyclopedia   (Site not responding. Last check: 2007-11-06)
Coherence is from Latin cohaerere = stick together, to be connected with, logically consistent.
Coherence is an attribute of physical quantities that can be described in terms of waves when a well-defined wavefront can be defined, as in classical optics.
Coherent (company) is a company specializing in equipment to make and measure coherent light.
en.wikipedia.org /wiki/Coherence   (185 words)

  
 Reference.com/Encyclopedia/Coherence (physics)
Spatial coherence is high for spherical waves and plane waves as it is related to the size and coherence of the light source.
A non-monochromatic point source of zero diameter emits spatially coherent light, while the light from a collection of incoherent point-sources which are resolved by the imaging system would have lower coherence (as the point sources are not coherent with each other, the resulting light has low spatial coherence).
The science of stellar interferometry measures the spatial coherence of starlight and uses it to determine which stars consist of two or more points (these are binaries or multiple stars) or to measure the diameter of stars.
www.reference.com /browse/wiki/Coherence_(physics)   (932 words)

  
 Quantum properties of light
Coherence is one of the unique properties of laser light.
This coherence is described in terms of temporal coherence and spatial coherence, both of which are important in producing the interference which is used to produce holograms.
There is a degree of coherence in sources like the mercury green line and some other useful spectral sources, but their coherence does not approach that of a laser.
hyperphysics.phy-astr.gsu.edu /hbase/optmod/qualig.html   (838 words)

  
 Optics - Biocrawler   (Site not responding. Last check: 2007-11-06)
Optics (appearance or look in ancient Greek) is a branch of physics that describes the behavior and properties of light and the interaction of light with matter.
Rays are bent at the interface between two dissimilar media, and may be curved in a medium in which the refractive index is a function of position.
The ray in geometric optics is perpendicular to the wavefront in physical optics.
www.biocrawler.com /encyclopedia/Optics   (480 words)

  
 Coherence in the Curriculum
For a number of years prior to 1995, the physics course taken by all first year engineering students at UCT was what I shall refer to as a traditional calculus based university physics course similar to the experience of many students in North America.
In discussions with the physics department, it became obvious that they conceptualized the objective of the first year physics quite differently from the way in which engineering was beginning to move.
The Physics Education Research (PER) literature is growing fast and the reader is encouraged to look at the reference by McDermott and Redish for an insight into the topics being researched with some comments by the authors.
www.aspect.uct.ac.za /documents/learn_phy.htm   (5084 words)

  
 [No title]
Coherence is a measure of the correlation that exists between the phases of the wave measured at different points.
The coherence of a wave depends on the characteristics of its source.
It is perfectly coherent in space and time, its coherence length and coherence time are both infinite.
electron9.phys.utk.edu /optics421/modules/m5/Coherence.htm   (994 words)

  
 science tour
In a new physics of life the phenomenae which were traditionally called "consciousness" (subject) and "material world" (object) naturally emerge from the physics of a perfectly embedded, superluminous and infinitely connected frequency system: the causal matrix.
So, although the physical elements may be perceived as grossly chaotic, their inner essence is each and every moment an instance of harmonic fusion as per the non-linear regime, perfectly in tune with all of creation.
In the new physics of Life, the concept of gravity is rather implied in the notion that matter (inertia) practically exists solely in mutual concomitance with (standard) space.
www.heartcoherence.com /sciencetour   (6331 words)

  
 Coherence * | Macroscopic Quantum Phenomena
The goal of this meeting is to bring together leading scientists from different subfields of condensed matter physics in order to advance the understanding of decoherence in nanostructures.
Recent developments in statistical physics and nonlinear dynamics have shed light on a new, sometimes counterintuitive role which noise plays in nonlinear systems: in a wide range of systems, random forces may bring a system to a more ordered state.
Chiarello evaluates the physical parameters for operation of a tunable flux qubit, calculating dissipation and decoherence factors, and discussing the potential for employment of integrated rapid single flux quantum (RSFQ) logic for qubit control.
superconducting.blogspot.com   (1833 words)

  
 What is the coherence length? What is the coherence time?
Coherence length is the space over which a wave is 'nicely' sinusoidal.
Coherence time is related to the classical uncertainty principle and is thus a little more complex.
The coherence time is approximately equal to 1/delta v, where delta v, is the bandwidth of the source.
www.physlink.com /Education/AskExperts/ae372.cfm   (210 words)

  
 Winners of the Nobel Prize in Physics
for his theoretical studies of the physical processes of importance to the structure and evolution of the stars.
for his decisive contributions to elementary particle physics, in particular the discovery of a large number of resonance states, made possible through his development of the technique of using hydrogen bubble chamber and data analysis.
for his investigations of the physics of the upper atmosphere especially for the discovery of the so-called Appleton layer.
almaz.com /nobel/physics/physics.html   (1991 words)

  
 vacuum coherence physics
The physics of the VCF essentially describes the manifestation of immanent qualities of the Vacuum, and forms a physics of interior, infinite connectedness, whereas classical physics describes the outer interaction of waves, particles and objects.
On the contrary, and in fact quite perpendicular to relativity theory, quantum physics does include a relative observer, that is, the observer became in some way part and parcel of a physical event, but it is staged within an absolute, linear time and space framework.
It is also utterly coherent with contemporary (eastern) intuitional science and will help to understand the difference between plain deterministic science and the way creation unfolds naturally, where life and individual perception are an inalienable part of physical reality.
www.heartcoherence.com /newscience   (1659 words)

  
 Physics and Astronomy - Past Colloquia Abstracts   (Site not responding. Last check: 2007-11-06)
Coherent control of a physical or chemical process can be achieved by preparing one of the initial reactants in a coherent superposition of two quantum states.
Medical physics is a branch of physics concerned with the application of physics to medicine.
I report on recent evidence for such a critical point in crystals of overdoped cuprates with a superconducting Tc of 60 K. At this critical concentration there is evidence of quantum disorder down to 10 K temperature as shown by a linear variation of the inverse lifetime of the carriers with temperature and frequency.
www.physics.yorku.ca /Colloquia/past_abstracts.html   (12138 words)

  
 Neutrino 'Coherence Length'?
The coherence length is the optical path length difference of a self interfering laserbeam which corresponds to a 50% fringe visibility, where the fringe visibility is defined as V = (Imax - Imin)/(Imax + Imin) and I is the fringe intensity.
Note that optical coherence is used in stellar interferometery as well as lasers - the key idea is that photons will have visible interference fringes as long as the difference in path lengths is not too great.
The coherence length is a measure of the maximum path length difference at which fringes will still occur.
www.physicsforums.com /showthread.php?p=983381#post983381   (259 words)

  
 Physics | The WWW Virtual Library
This encyclopedia explains basic terms and principles of laser physics and technology, with some content added from other topics such as general optics, nonlinear optics, and quantum optics.
Information sources for Nuclear Physics research institutes and accelerator facilities - This list is originally based on the HEP list, modified by adding nuclear physics research institutes and universities.
Plasma science and technology are multilevel, multifacted, and multimedia as demonstrated here by diverse and comprehensive links to references, subjects, societies, publications, conferences, funding sources, formulary, glossary, newsgroups, and a broad-based Coalition for Plasma Science founded to increase public awareness and understanding of the plasma sciences and their many applications and benefits to society.
vlib.org /Physics   (347 words)

  
 AllRefer.com - coherence (Physics) - Encyclopedia
coherence, constant phase difference in two or more Waves over time.
Coherence underlies a variety of physical phenomena, such as interference and diffraction.
Coherence is also responsible for many of the remarkable properties of laser radiation; laser light is coherent, which is to say that the light waves from a laser are all in phase.
reference.allrefer.com /encyclopedia/C/coherenc.html   (197 words)

  
 Encyclopedia of Laser Physics and Technology - coherence, coherent, light, spatial and temporal coherence
Coherence is one of the most important concepts in optics and is strongly related to the ability of light to exhibit interference effects.
Lasers have the potential to generate beams with very high temporal and/or spatial coherence, and this is perhaps the most fundamental difference between laser radiation and radiation from other light sources.
In quantum optics, the term coherence is often used for the state of light-emitting atoms or ions.
rp-photonics.com /coherence.html   (763 words)

  
 Coherence (physics) Encyclopedia Articles @ LaunchBase.org (Launch Base)   (Site not responding. Last check: 2007-11-06)
Coherence (physics) Encyclopedia Articles @ LaunchBase.org (Launch Base)
As an example, consider two waves perfectly correlated for all times.
For polarized light the end of the vector lies on the surface of the sphere, whereas the vector has zero length for unpolarized light.
www.launchbase.org /encyclopedia/Coherence_(physics)   (1968 words)

  
 [No title]   (Site not responding. Last check: 2007-11-06)
In the following I briefly summarize a characterization of conceptual coherence and a teaching approach aimed at enhancing students' conceptual coherence in physics.
If a student has representational coherence he is able to use multiple representations and move between them.
Sabella, M. Using the context of physics problem solving to evaluate the coherence of student knowledge.
kotisivu.mtv3.fi /physics/research.html   (480 words)

  
 Encyclopedia of Laser Physics and Technology - coherence length, nonlinear optics
The coherence length can be used to quantify the degree of temporal (not spatial!) coherence as the propagation length (and thus propagation time) over which coherence degrades significantly.
It is defined as the coherence time times the vacuum velocity of light.
An unfortunate use of the term coherence length is common in nonlinear optics: for example, in second-harmonic generation, one often defines as coherence length the length over which fundamental and harmonic wave get out of phase.
www.rp-photonics.com /coherence_length.html   (303 words)

  
 Optical "coherence"
If we pass the light from a laser through a stack of frosted plates, is the result still "coherent light?" For most optical applications requiring coherent light, this type of heavily diffused laser light is fairly useless.
A spatial filter thinks it's incoherent: pass it through a lens with a pinhole at the focus nearly all the light will be blocked.
Somehow the textbook definition of coherence doesn't seem correct when it declares diffuse laser light to be coherent light.
www.physicsforums.com /showthread.php?t=72401   (187 words)

  
 UMD PERG PhD Dissertations: Sabella
We use the context of problem solving to show that students exhibit a local coherence but not global coherence in their physics knowledge.
Although the schemas students develop in the physics course are usually sufficient in the class, they are often insufficient for solving complex problems.
Physics Education Research (PER) has shown that students in introductory physics lack a deep understanding of physics principles and concepts.
www.physics.umd.edu /ripe/perg/dissertations/Sabella   (449 words)

  
 Amazon.com: Optical Coherence and Quantum Optics: Books: Leonard Mandel,Emil Wolf   (Site not responding. Last check: 2007-11-06)
This book is a systematic treatment of one of these fields--the broad area that deals with the coherence and fluctuation of light.
The authors begin with a review of probability theory and random processes, and follow this with a thorough discussion of optical coherence theory within the framework of classical optics.
The sound introduction to coherence theory and the quantum nature of light and the chapter-end exercises will appeal to graduate students and newcomers to the field.
www.amazon.com /exec/obidos/tg/detail/-/0521417112?v=glance   (993 words)

  
 Polarisation-sensitive optical coherence tomography of Collagen
It acts as the “scaffolding” of the extra-cellular matrix and gives skin, tendon, cartilage and intervertebral discs their mechanical strength.
Alterations in its physical properties underlie many important pathological processes in the body such as scar tissue formation, osteoarthritis and back pain.
Polarization-sensitive optical coherence tomography combines polarimetry with low coherence reflectometry to provide high-resolution optically sectioned images of the birefringence of intact tissues.
newton.ex.ac.uk /research/biomedical/optics/psoct.html   (520 words)

  
 XXIInd International School on Theoretical Physics
Once observed, they shed new light on the role of quantum coherence and many-body effects in systems of reduced geometry as well as on the microscopic origin of dephasing, dissipation, and noise.The coherent phenomena described above should be confronted with various aspects of quantum coherence found in macroscopic superconductors.
The disscusion of specialists from two different fields should shed more light on the intriguing problem of quantum coherence.
Our University coach is going to take the participants from the Institute of Physics in Katowice, Uniwersytecka 4 to Ustron at 4 p.m.
server.phys.us.edu.pl /thschool/index.php3   (407 words)

  
 Encyclopedia Nanotech   (Site not responding. Last check: 2007-11-06)
The science (and corresponding technology) that seeks to understand (and control) the atomic and molecular structure of matter.
From quantum physics, coherence is a property exhibited by matter and energy when it remains unmeasured and is thus able to exist in more than one state simultaneously (superposition).
A substance, material or object that allows energy to flow through it with low resistance.
www.quantumcad.com /pages/encyclopedia.php?fletter=C   (169 words)

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