What does negative permeability mean?
Negative magnetic permeability is when a material, in response to an imposed magnetic field, forms a magnetic dipole in the opposite direction to the imposed field. As regards PLASMA in a Magnetic Field the particles gyration results in a magnetic moment countering the external field. Therefore plasma is diamagnetic.
Can refractive index is negative?
For all known naturally occurring materials the refractive index assumes only positive values. In 1967 Soviet physicist Victor Veselago hypothesized that a material with a negative refractive index could exist without violating any of the laws of physics.
What is negative phase velocity?
In a negative phase velocity medium, the phase velocity is directed opposite to the direction of energy flow (and attenuation).
What is K in phase velocity?
The phase velocity is: vp = ω/k. The function ω(k), which gives ω as a function of k, is known as the dispersion relation. If ω is directly proportional to k, then the group velocity is exactly equal to the phase velocity. A wave of any shape will travel undistorted at this velocity.
What is the difference between phase velocity and group velocity?
Waves can be in the group and such groups are called wave packets, so the velocity with a wave packet travels is called group velocity. The velocity with which the phase of a wave travels is called phase velocity.
What is the difference between wave velocity and group velocity?
In the analysis, when a source is placed in medium or a vacuum, such that there is an emission of radiation in the form of electromagnetic waves, then the velocity of possessed by waves collectively is called Group velocity, and an individual component of velocity for a particular wave is called wave velocity.
Is phase velocity faster than light?
The phase velocity vp can be less than the speed of light. It can also be greater than the speed of light, but this does not violate special relativity because the single monochromatic wave or constant oscillation does not carry energy or information.
Is phase velocity faster than C?
Phase velocities above c The phase velocity of an electromagnetic wave, when traveling through a medium, can routinely exceed c, the vacuum velocity of light. For example, this occurs in most glasses at X-ray frequencies.
What is the physical meaning of phase velocity?
The phase velocity of a wave is the rate at which the wave propagates in some medium. This is the velocity at which the phase of any one frequency component of the wave travels. For such a component, any given phase of the wave (for example, the crest) will appear to travel at the phase velocity.
What is the speed of light underwater?
The refractive index of a material is defined as the ratio of speed of light in vaccum to the speed of light in medium. Refractive index of water is 1.3. So theoretically speed of light in water is 230769 km/s .
Which one is greater phase velocity and group velocity?
Phase velocity: In a normal medium, the phase velocity is greater than the group velocity.
Why should a matter wave move with group velocity and not phase velocity?
The phase velocity actually don’t carry any meaningful physical information for matter wave. So the velocity of the particle is determined by the group velocity, not phase velocity. Now since phase velocity does not carry any physical signal, so it can have speed greater than light.
In which medium phase velocity and group velocity are equal?
Dispersion. When these two monochrome waves are propagating in vacuum, they have the same phase velocity c (the speed of light in vacuum), and the superposed wave’s phase velocity equals its group velocity(both are c).
What is the relationship between phase and group velocity for a non relativistic free particle?
The product between the phase velocity and the group velocity of any particle (massive or massless) equals the square of the speed of light in vacuum. The group velocity of any particle (massive or massless) is equal to the derivative of its total relativistic energy with respect to its relativistic momentum. 2.
Which velocity has no physical meaning for matter waves?
Thus, the phase velocity cannot have a physical interpretation. 3.2 Waves of What?