FACTOID # 3: South Carolina has the highest rate of violent crimes and aggravated assaults per capita among US states.
 
 Home   Encyclopedia   Statistics   States A-Z   Flags   Maps   FAQ   About 
   
 
WHAT'S NEW
 

SEARCH ALL

FACTS & STATISTICS    Advanced view

Search encyclopedia, statistics and forums:

 

 

(* = Graphable)

 

 


Encyclopedia > Phase velocity

The phase velocity of a wave is the rate at which the phase of the wave propagates in space. This is the velocity at which the phase of any one frequency component of the wave will propagate. You could pick one particular phase of the wave (for example the crest) and it would appear to travel at the phase velocity. The phase velocity is given in terms of the wave's angular frequency ω and wave vector k by Surface waves in water This article is about waves in the most general scientific sense. ... This article is about a portion of a periodic process. ... It has been suggested that this article or section be merged into Angular velocity. ... A wave vector is a vector that represents two properties of a wave: the magnitude of the vector represents wavenumber (inversely related to wavelength), and the vector points in the direction of wave propagation. ...

v_mathrm{p} = frac{omega}{k}

Note that the phase velocity is not necessarily the same as the group velocity of the wave, which is the rate that changes in amplitude (known as the envelope of the wave) will propagate. The group velocity of a wave is the velocity with which the variations in the shape of the waves amplitude (known as the modulation or envelope of the wave) propagate through space. ...


The phase velocity of electromagnetic radiation may under certain circumstances (e.g. in the case of anomalous dispersion) exceed the speed of light in a vacuum, but this does not indicate any superluminal information or energy transfer. It was theoretically described by physicists such as Arnold Sommerfeld and Leon Brillouin. See dispersion for a full discussion of wave velocities. Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... Dispersion of a light beam in a prism. ... The speed of light in a vacuum is an important physical constant denoted by the letter c for constant or the Latin word celeritas meaning swiftness.[1] It is the speed of all electromagnetic radiation, including visible light, in a vacuum. ... Faster-than-light (also superluminal or FTL) communications and travel are staples of the science fiction genre. ... Arnold Johannes Wilhelm Sommerfeld (December 5, 1868 in Königsberg, East Prussia – April 26, 1951 in Munich, Germany) was a German physicist who introduced the fine-structure constant in 1919. ... Léon N. Brillouin ( August 7, 1889- 1969) was a French physicist. ... Dispersion of a light beam in a prism. ...

Contents

Matter wave phase

In quantum mechanics, particles also behave as waves with complex phases. By the de Broglie hypothesis, we see that For a less technical and generally accessible introduction to the topic, see Introduction to quantum mechanics. ... In mathematics, a complex number is a number of the form where a and b are real numbers, and i is the imaginary unit, with the property i 2 = −1. ... In physics, the de Broglie hypothesis is the statement that all matter (any object) has a wave-like nature (wave-particle duality). ...

v_mathrm{p} = frac{omega}{k} = frac{E/hbar}{p/hbar} = frac{E}{p} .

Using relativistic relations for energy and momentum, we have Albert Einsteins theory of relativity is a set of two theories in physics: special relativity and general relativity. ...

v_mathrm{p} = frac{E}{p} = frac{gamma m c^2}{gamma m v} = frac{c^2}{v} = frac{c}{beta}

where E is the total energy of the particle (i.e. rest energy plus kinetic energy in kinematic sense), p the momentum, γ the Lorentz factor, c the speed of light, and β the velocity as a fraction of c. The variable v can either be taken to be the velocity of the particle or the group velocity of the corresponding matter wave. See the article on group velocity for more detail. Since the particle velocity v < c for a massive particle according to special relativity, phase velocity of matter waves always exceed c, i.e. In classical physics, the total energy of an object is the sum of its potential energy and its kinetic energy. ... The term mass in special relativity is used in a couple of different ways, occasionally leading to a great deal of confusion. ... The cars of a roller coaster reach their maximum kinetic energy when at the bottom of their path. ... In physics, kinematics is the branch of mechanics concerned with the motions of objects without being concerned with the forces that cause the motion. ... This article is about momentum in physics. ... It has been suggested that Lorentz term be merged into this article or section. ... The speed of light in a vacuum is an important physical constant denoted by the letter c for constant or the Latin word celeritas meaning swiftness.[1] It is the speed of all electromagnetic radiation, including visible light, in a vacuum. ... The group velocity of a wave is the velocity with which the variations in the shape of the waves amplitude (known as the modulation or envelope of the wave) propagate through space. ... For a less technical and generally accessible introduction to the topic, see Introduction to special relativity. ...

v_mathrm{p} > c ,,

and as we can see, it approaches c when the particle velocity is in the relativistic range. The superluminal phase velocity does not violate special relativity, for it doesn't carry any information. See the article on signal velocity for detail. Albert Einsteins theory of relativity is a set of two theories in physics: special relativity and general relativity. ... Faster-than-light (also superluminal or FTL) communications and travel are staples of the science fiction genre. ... The signal velocity of a wave is the speed at which a pulse travels through a medium. ...


External links

  • Subluminal, a Java applet
  • Group and Phase Velocity - Java applet showing the difference between group and phase velocity.

See also

The group velocity of a wave is the velocity with which the variations in the shape of the waves amplitude (known as the modulation or envelope of the wave) propagate through space. ... Wave propagation refers to the ways waves travel through a medium (waveguide). ...

References

  • Tipler, Paul A. and Ralph A. Llewellyn (2003). Modern Physics. 4th ed. New York; W. H. Freeman and Company. ISBN 0-7167-4345-0. 222-3 pp.
  • Leon Brillouin "Wave Propagation And Group Velocity" Academic Press Inc., New York and London (1960) ISBN 0-1213-4968-3.
  • Main, Iain G. (1988).Vibrations and Waves in Physics. 2nd ed. New York; Cambridge University Press. ISBN 0-5212-7846-5. 214-6 pp.


Léon N. Brillouin ( August 7, 1889- 1969) was a French physicist. ...

Velocities of Waves
Phase velocity | Group velocity | Front velocity | Velocity of energy transfer | Signal velocity | Information velocity

  Results from FactBites:
 
Phase Velocity - Microwave Encyclopedia - Microwaves101.com (150 words)
Phase velocity is the speed at which microwave energy travels along a transmission line.
Velocity for a traveling wave is equal to the speed of light divided by the square root of the effective relative permittivity.
Phase velocity can also be devived from the inductance and capacitance per unit length of a transmission line.
Phase velocity - Wikipedia, the free encyclopedia (305 words)
The phase velocity of a wave is the rate at which the phase of the wave propagates in space.
Note that the phase velocity is not necessarily the same as the group velocity of the wave, which is the rate that changes in amplitude (known as the envelope of the wave) will propagate.
The phase velocity of electromagnetic radiation may under certain circumstances exceed the speed of light in a vacuum, but this does not indicate any superluminal information or energy transfer.
  More results at FactBites »

 
 

COMMENTARY     


Share your thoughts, questions and commentary here
Your name
Your comments

Want to know more?
Search encyclopedia, statistics and forums:

 


Press Releases |  Feeds | Contact
The Wikipedia article included on this page is licensed under the GFDL.
Images may be subject to relevant owners' copyright.
All other elements are (c) copyright NationMaster.com 2003-5. All Rights Reserved.
Usage implies agreement with terms, 1022, m