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Topic: Dispersion

  Dispersion (optics) - Wikipedia, the free encyclopedia
In optics, dispersion is a phenomenon that causes the separation of a wave into spectral components with different frequencies, due to a dependence of the wave's speed on its frequency.
The overall dispersion of the optical resonator is a major factor in determining the duration of the pulses emitted by the laser.
In the technical terminology of gemology, dispersion is the difference in the refractive index of a material at the B and G Fraunhofer wavelengths of 686.7 nm and 430.8 nm and is meant to express the degree to which a prism cut from the gemstone shows fire or color.
en.wikipedia.org /wiki/Dispersion_(optics)   (1216 words)

As the light is twice refracted, the dispersion is increased, and the rays, after transmission through the prism, form a divergent system, which may be allowed to fall on a sheet of white paper, forming the wellknown solar spectrum.
Dispersive Power.In order to find the amount of dispersion caused by any given prism, the deviations produced by it on two rays of any definite pure colors may be measured.
By studying the dispersion of colors in water, turpentine and crown glass Newton was led to suppose that dispersion is proportional to refraction.
74.1911encyclopedia.org /D/DI/DISPERSION.htm   (2350 words)

 Dispersion - Wikipedia, the free encyclopedia
A phenomenon that causes the separation of a wave into components of varying frequency.
When dealing with optical fibres there can also be dispersion of different modes in the fibre and of different polarizations.
In mass transfer, Dispersive mass transfer is spreading of mass from highly concentrated areas to lower concentrated areas.
en.wikipedia.org /wiki/Dispersion   (184 words)

 Dispersion   (Site not responding. Last check: 2007-10-22)
Dispersion is the phenomenon which gives you the separation of colors in a prism.
Usually the dispersion of a material is characterized by measuring the index at the blue F line of hydrogen (486.1 nm), the yellow sodium D lines (589.3 nm), and the red hydrogen C line (656.3 nm).
Dispersion in optical glasses is typically characterized by index of refraction values at three standard wavelengths.
hyperphysics.phy-astr.gsu.edu /hbase/geoopt/dispersion.html   (242 words)

 DISPERSION   (Site not responding. Last check: 2007-10-22)
Dispersion is the spreading of a solute, colloidal suspension, or temperature caused by variations in fluid velocity about the mean (or barycentric) velocity.
is the diffusion coefficient in the fluid, α is the dispersivity or the dispersion length, and v is the average linear velocity.
The presence of an immobile gas phase leads to a decrease in dispersion because the gas bubbles tend to be trapped in the larger pores.
www.geo.utexas.edu /courses/346c/dispersion.htm   (922 words)

 Dispersion - Microwave Encyclopedia - MicroWaves101.com
For wideband signals, you may have to worry about the effects of dispersion distorting your signal, for example, when you are trying to put a one nanosecond pulse through a waveguide near the lower cutoff frequency, you could be in a heap of trouble.
The dispersion of microstrip is just a few percent over a moderate frequency band, and can often be ignored.
This is because the effective dielectric constant of CPW is roughly equal to (1+ER)/2, or the average of free space and the substrate dielectric constant, or 1.65 in this case.
www.microwaves101.com /encyclopedia/dispersion.cfm   (408 words)

 DISPERSION, THE in the Bible Encyclopedia - ISBE (Bible History Online)
That the Dispersion of the Jews was for the benefit of the Gentiles is a conception to which expression is given in utterances of psalmists and prophets (Ps 67; Mic 5:7, etc.).
The Eastern Dispersion, caused by the Assyrian and Babylonian captivities, seems to have increased and multiplied, and to have enjoyed a considerable measure of liberty, and of prosperity.
Of the widespread distribution of the Dispersion in Asia Minor there is abundant testimony, not only in the texts of the apostles, but in classical and early Christian literature and in the epigraphic literature which has been accumulating for the last 30 years.
www.bible-history.com /isbe/D/DISPERSION,+THE   (5032 words)

 AllRefer.com - dispersion, in chemistry (Chemistry) - Encyclopedia
dispersion, in chemistry, mixture in which fine particles of one substance are scattered throughout another substance.
A dispersion is classed as a suspension, colloid, or solution.
Generally, the particles in a solution are of molecular or ionic size; those in a colloid are larger but too small to be observed with an ordinary microscope; those in a suspension can be observed under a microscope or with the naked eye.
reference.allrefer.com /encyclopedia/D/dispers-che.html   (197 words)

 Telephony: Bandwidth; DEFEATING Dispersion - Technology Information   (Site not responding. Last check: 2007-10-22)
Dispersion compensating fiber is a spool of fiber several meters long that has fixed values of dispersion, which cancel out the fixed values of dispersion on the carrier fiber.
The dispersion compensating fiber is placed inside an amplifier where it cancels chromatic dispersion's effects as a light pulse on multiple channels passes through it.
However, because dispersion compensating fiber initially was created to diminish chromatic dispersion on a single wavelength, when it is used on a fiber carrying multiple wavelengths, it typically is set to correct chromatic dispersion most accurately on the center wavelength.
www.findarticles.com /p/articles/mi_m0TPY/is_2000_Dec_4/ai_67832039   (1267 words)

 AgWeather - Models - Dispersion
With respect to dispersion conditions, the Oklahoma Dispersion Model is used in conjunction with weather conditions reported by the Oklahoma Mesonet to produce a map of current dispersion conditions across Oklahoma.
For short distances (less than 10 km or 6 miles), the dispersion of gas and small particulates is typically modeled by the Gaussian distribution, where the horizontal width of the pollutant plume has a "normal" distribution with standard deviation "sigma-y" and the vertical depth of the plume has a similar distribution with standard deviation "sigma-z".
This scheme is thus conservative in the sense that the dispersion categories "protect" nearby sensitive areas in the path of the center of the plume; the wind may not carry the plume to a particular area, but if it does, these would be the resulting pollutant concentrations at that site.
agweather.mesonet.ou.edu /models/dispersion/description.html   (1170 words)

 Dispersion in Wavelength   (Site not responding. Last check: 2007-10-22)
On the positive side, it is the basis for the prism and its ability to separate light according to wavelength; on the negative side, it is the source of chromatic aberration in optical devices (the failure of different wavelengths to focus at the same point).
Dispersion is the basis for the prism and its ability to spatially separate light according to wavelength, as illustrated in the following animation.
Although a prism can disperse light according to color, in modern spectrographs it is more common to accomplish the same task by using a diffraction grating.
csep10.phys.utk.edu /astr162/lect/light/dispersion.html   (271 words)

 IEC: Light without Limits: Taming Dispersion in Tomorrow's High-Speed Networks
As described in Topic 1, CD, slope dispersion, and PMD cause waveforms within optical fibers to spread out, lose their shape, and become difficult to detect by receivers at the end of a fiber span.
Slope mismatch dispersion is a subset of chromatic dispersion.
Given the complexity of the dispersion challenge and the fact that its real-world impact is only beginning to be experienced and understood, three principles are emerging that promise to help companies address dispersion globally, throughout the network.
www.webproforum.com /online/tutorials/light_limit/topic03.html   (1502 words)

 Bambooweb: Dispersion (optics)
In optics, dispersion is a phenomenon that causes the separation of a wave into components with different frequencies, due to a dependence of the wave's speed on its frequency.
One possible answer to this problem is to send signals down the optical fibre with a wavelength of ~1.3 μm; this is a wavelength at which GVD is zero in silica glass, so pulses at this wavelength suffer minimal spreading from dispersion.
Another possible option is to use soliton pulses, a form of optical pulse which uses a nonlinear optical effect to self-maintain its shape.
www.bambooweb.com /articles/d/i/Dispersion_(optics).html   (1060 words)

 London Dispersion Forces   (Site not responding. Last check: 2007-10-22)
The London dispersion force is a temporary attractive force that results when the electrons in two adjacent atoms occupy positions that make the atoms form temporary dipoles.
Dispersion forces are present between any two molecules (even polar molecules) when they are almost touching.
Dispersion forces are present between all molecules, whether they are polar or nonpolar.
www.chem.purdue.edu /gchelp/liquids/disperse.html   (336 words)

 Dispersion   (Site not responding. Last check: 2007-10-22)
This variation of the refractive index with the wavelength or frequency of the light is called dispersion.
The color of green flashes is due to the dispersion of air, which makes atmospheric refraction slightly different for different parts of the spectrum.
The dispersion of air, like that of water, glass, clear plastics, and most other materials, is small: the refractivity (n - 1) varies by about 1% across the visible spectrum.
mintaka.sdsu.edu /GF/explain/optics/disp.html   (201 words)

 CHEST: QT dispersion: much ado about something?   (Site not responding. Last check: 2007-10-22)
QT dispersion is measured as the difference between the maximal and minimal QT intervals.
Since elevated heart rate itself is associated with increased risk of death in the general population, analysis of QT dispersion should probably not be rate corrected to eliminate the influence from an additional variable.
In a retrospective study (32) of 219 patients with diabetes mellitus, increased QT dispersion was associated with an increased incidence of myocardial ischemia and left ventricular hypertrophy.
www.findarticles.com /p/articles/mi_m0984/is_6_125/ai_n6151110   (1470 words)

 Laser Dispersion Experiment   (Site not responding. Last check: 2007-10-22)
The dispersion curves are both scaled in order to make them more clearly visible next to the large drive signal--this graph is mostly for qualitative reference.
While the effects we saw were weaker than we had expected, they still serve to show visually what dispersion and absorption are, and how they change when the technique of saturated absorption is applied.
Saleh and Teich, "Absorption and Dispersion", Fundamentals of Photonics, 1991, 174-182 and 928-931.
www.phy.davidson.edu /StuHome/blreynolds/Dispersion/analysis.htm   (339 words)

Material dispersion occurs because the spreading of a light pulse is dependent on the wavelengths' interaction with the refractive index of the fiber core.
Waveguide dispersion occurs because the mode propagation constant (andbeta;) is a function of the size of the fiber's core relative to the wavelength of operation.
The total dispersion present in single mode fibers may be minimized by trading material and waveguide properties depending on the wavelength of operation.
www.tpub.com /neets/tm/106-15.htm   (523 words)

 Error Propagation in Air Dispersion Modeling
A host of assumptions and constraints are required to derive the Gaussian dispersion equation for modeling a continuous, buoyant plume from a single point-source in flat terrain...
The accuracy of the dispersion coefficients (i.e., the vertical and horizontal standard deviations of the emission distribution) used in the Gaussian dispersion equation.
Deriving the Gaussian dispersion equation requires the assumption of constant conditions for the entire plume travel distance from the emission source point to the downwind ground-level receptor.
www.air-dispersion.com /feature.html   (2272 words)

 Dispersive Waves
Most waves in material media are dispersive, however, and wave forms originally set up are bound to change in a manner that the wave energy is more spatially spread out or dispersed.
Animation 3 shows superposition of two sinusoidal waves in dispersive case, sin(x - t) + sin(1.2x - 1.1t) (group velocity = half of phase velocity), while the last animation shows the case of nondisperve wave, sin(x - t) + sin(1.2x - 1.2t).
Note that in the dispersive case (Animation 3), wave propagation is not simple parallel shift.
physics.usask.ca /~hirose/ep225/animation/dispersion/anim-dispersion.html   (270 words)

 dispersion --  Encyclopædia Britannica
Although the term refers to the physical dispersal of Jews throughout the world, it also carries religious, philosophical, political, and eschatological connotations, inasmuch as the Jews...
Dispersion formulas for gases have been obtained by assuming that the atoms or molecules contain bound electrons having a response that varies with frequency in the manner described above.
The two main classes of optical glass are crown glass, which has low refraction and dispersion, and flint glass, which has high refraction and dispersion.
www.britannica.com /eb/article-9030640?tocId=9030640&query=dispersion   (707 words)

 Dispersion Forces
The London dispersion forces are a universal component of long-range vdW forces and arise from the electronic structure of materials and their optical behavior.
The close relationship between the London dispersion forces and the material’s chemistry and electronic structure represents an avenue for materials design as has been exploited in ceramics processing and applications.
Finally, new results on the effects of retardation of the London dispersion interaction at large distances are discussed with an emphasis on novel wetting phenomena such as equilibrium surficial films of water on ice and bimodal wetting/dewetting systems.
www.lrsm.upenn.edu /~frenchrh/dispersion_forces.htm   (266 words)

 Velocity dispersion measurements - SDSS DR3
The velocity dispersion is a fundamental parameter because it is an observable which better quantifies the potential well of a galaxy.
The SDSS velocity dispersion estimates are obtained by fitting the restframe wavelength range 4000-7000 Å, and then averaging the estimates provided by the "Fourier-fitting" and "Direct-fitting" methods.
Therefore, the estimated velocity dispersions of more distant galaxies are affected by the motions of stars at larger physical radii than for similar galaxies which are nearby.
www.sdss.org /dr3/algorithms/veldisp.html   (1127 words)

 AgWeather - Models - Dispersion
The focus of the Model is the evaluation of dispersion conditions with respect to downwind concentrations at distances of 1/4 mile and greater.
Based on the current or forecasted weather conditions, the Oklahoma Dispersion Model assigns a "Dispersion Condition", which is reflective of downwind concentrations at distances of 1/4 mile or greater.
The dispersion condition maps (or MOS-based text output) should be used to assess the atmosphere's ability to disperse near-surface releases of gases and particulates, while the weather maps (or MOS-based text output) should be used to assess the direction the gases and particulates will drift.
agweather.mesonet.ou.edu /models/dispersion/howtousemodel.html   (1620 words)

 Planar theory
It is said that the higher frequencies beam (like headlights) instead of disperse waves like ripples in a pool at the lower frequencies.
Thus, it disperses all frequencies it was asked to reproduce as if from a comparatively small driver, or point.
This reduced dispersion is why line-sources sound louder at a distance.
www.integracoustics.com /MUG/MUG/articles/sources   (869 words)

 Air Dispersion Modeling   (Site not responding. Last check: 2007-10-22)
Developed by the United Kingdom's Meteorological Office, the NAME model is part of the contingency plans in the event of accidental releases of radioactivity into the atmosphere: to provide early warning for the guidance of emergency services; and to predict concentrations, depositions and dosages of radionuclides as input to impact assessments.
Within the program, a Pollution Dispersion team: studies the Lagrangian theory of turbulent dispersion; conducts laboratory and field studies of convective boundary layer growth, turbulence, and dispersion; and develops advanced air dispersion models utilizing ideas from the Lagrangian theory studies and from the laboratory and field studies.
The committee's purpose is to review current understanding of atmospheric dispersion and to identify suitable models for use primarily in authorization or licensing, in the context of atmospheric discharges from nuclear industry activities.
www.medlina.com /air_dispersion_modeling.htm   (1951 words)

Dispersion is the manner in which the frequency and the wave number are related in a medium.
Light waves have a linear dispersion in a vacuum but in water they have a nonlinear dispersion.
This nonlinear dispersion can cause a white light spectrum to be changed into a rainbow.
webphysics.davidson.edu /faculty/dmb/bernstein/qmwave/section2d.html   (294 words)

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