Effect of electrical permittivity on the speed of light

In summary, the question is why an increased electrical permittivity decreases the phase velocity of light in a medium and what interactions are seen on an atomic level. The person is aware of the equation relating speed of light to electrical permittivity and magnetic permeability, but does not understand their relationship and is looking for resources or answers.
  • #1
Muggo
Why does an increased electrical permittivity reduce the phase velocity of light in a medium? Furthermore, what interactions do we see on an atomic level?

I am aware of the equation that defines the speed of light in terms of the electrical permittivity and magnetic permeability, but I do not understand their relationship.

Many thanks to anyone who is able to answer this question or/and refer me to a resource where I can obtain an answer! :smile:
 
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  • #2
Have you tried Wikipedia or any of the other well known sites? Google is often a very good start and anyone can use it.
 
  • #3
Muggo said:
Why does an increased electrical permittivity reduce the phase velocity of light in a medium? Furthermore, what interactions do we see on an atomic level?

I am aware of the equation that defines the speed of light in terms of the electrical permittivity and magnetic permeability, but I do not understand their relationship.

Many thanks to anyone who is able to answer this question or/and refer me to a resource where I can obtain an answer! :smile:
You already have a thread going on this question. Please do not cross-post across the PF forums. This copy is now locked.

https://www.physicsforums.com/threa...al-permittivity-on-the-speed-of-light.923520/
 

1. How does electrical permittivity affect the speed of light?

The electrical permittivity of a medium affects the speed of light by determining how much the electric field can penetrate the material. In a medium with a higher permittivity, the electric field experiences more resistance, resulting in a slower speed of light.

2. What is the relationship between electrical permittivity and the speed of light?

The speed of light is inversely proportional to the square root of the electrical permittivity of a medium. This means that as the permittivity increases, the speed of light decreases, and vice versa.

3. How does the speed of light change in different materials with varying electrical permittivity?

The speed of light can vary greatly in different materials due to their differing electrical permittivities. In a vacuum, the speed of light is approximately 299,792,458 meters per second. However, in materials such as glass or water, the speed of light can decrease to around 75-80% of its speed in a vacuum due to their higher permittivities.

4. Can the speed of light be faster than the speed of light in a vacuum due to electrical permittivity?

No, the speed of light in a vacuum is considered the maximum speed at which anything can travel in the universe. Even in materials with very low permittivities, the speed of light cannot exceed the speed of light in a vacuum.

5. How does electrical permittivity affect the behavior of light in optical fibers?

The electrical permittivity of the material used in optical fibers is an important factor in determining how efficiently light can be transmitted through them. Materials with higher permittivities can cause more light to be reflected back into the fiber, leading to loss of signal. Therefore, materials with lower permittivities are preferred for use in optical fibers to minimize signal loss.

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