Permittivity and Permeability affect propagation velocity?

In summary, the speed of light in a medium is affected by both permittivity and permeability, as stated by the linked website and confirmed by an expert in the field, Richard Blade. This is due to the delay caused by photon absorption and re-emission, as well as the scattering of the incident wave inside the medium. This reduction in speed is predicted both mathematically and through microscopic observations.
  • #1
jmatejka
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If I understand correctly in refraction, photon absorption and re-emission accounts for light taking "longer" to travel.

Regarding Permeability and Permittivity, the below linked website states:


"permittivity affects the speed of propagation of a wave through a medium"

http://www.antenna-theory.com/definitions/permittivity.php

AND

"permeability also affects the speed of propagation of an electromagnetic wave in a medium"

http://www.antenna-theory.com/definitions/permeability.php



Googling didnt lead me to any supportive information, do the statements make any sense?

Thanks, John
 
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  • #3
I am aware of the speed of light, my question is if anything unusual is going on with permittivity and permeability that could account for "apparent" change in velocity, as refraction does.

I also hopefully understand refraction is dealing with the photon and my question pertains to E&M fields.

If you believe the page to be in error please say so, Thanks, John
 
Last edited:
  • #4
jmatejka said:
I am aware of the speed of light, my question is if anything unusual is going on with permittivity and permeability that could account for "apparent" change in velocity, as refraction does.

If you followed the link, it should be pretty obvious that the speed of propagation is directly related to the product of the quantities in question. If that is not what you are looking for, then I have no idea what you are asking about; you may want to rephrase your question.
 
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  • #5
If anyone is interested, below is a reply to my question from my friend Richard Blade, former Chair of the Physics Dept, University of Colorado at Colorado Springs:

John-

All the statements you quoted are true. Macrosopically and mathematically, the speed of light in a transparent medium is one over the square root of the product of the permittivity and the permeability. That comes about by deriving the wave equation from Maxwell's equations. From the microscopic view, you can imagine that the incident EM wave is being scattered inside the medium, and that the scattered wave is slightly delayed from the incident wave, thereby making the composite wave front slightly slower (during the period of absorption and re-emission) than the incident wave front. The math, although looking quite different, predicts exactly the same reduction in speed as the macroscopic.

Richard

This seems to be an elaboration to what was stated above by Voko. Thanks, Regards, John
 

1. What is permittivity and permeability?

Permittivity is the measure of a material's ability to store an electric charge, while permeability is the measure of a material's ability to support the formation of a magnetic field. Both of these properties affect how electromagnetic waves propagate through a material.

2. How do permittivity and permeability affect propagation velocity?

Permittivity and permeability have a direct impact on the speed at which electromagnetic waves travel through a material. Generally, the higher the permittivity and permeability of a material, the slower the propagation velocity will be. This is because these properties affect how easily an electromagnetic wave can travel through a material.

3. What is the relationship between permittivity and permeability?

Permittivity and permeability are related to each other in a phenomenon known as Maxwell's equations. These equations describe the behavior of electromagnetic fields and show that permittivity and permeability are inversely proportional to each other. This means that as one property increases, the other decreases.

4. How do different materials affect the propagation velocity of electromagnetic waves?

Different materials have different permittivity and permeability values, which in turn affect the propagation velocity of electromagnetic waves. Materials with high permittivity and permeability, such as metals, will slow down the propagation velocity, while materials with low permittivity and permeability, such as air, will allow electromagnetic waves to travel at faster speeds.

5. Why is understanding the impact of permittivity and permeability on propagation velocity important?

Understanding the relationship between permittivity, permeability, and propagation velocity is crucial in various fields, including telecommunications, radar technology, and medical imaging. It allows us to predict and control how electromagnetic waves will behave in different materials, which is essential for designing and optimizing various devices and technologies.

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