Light in a medium - Question about the FAQ

In summary, the FAQ section states that light can be slower in a medium when its frequency is beyond the phonon spectrum. However, if the frequency falls within the spectrum, the light will move at the speed of c without being slowed down by the medium. This can depend on the material, with some materials causing the light to be absorbed and dissipated as heat due to vibrational modes, while others may interact with electronic excitations. In general, light is slower than the speed of light in vacuum, even above the phonon spectrum.
  • #1
bubblewrap
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2
In the FAQ section 'Do Photons Move Slower in a Solid Medium?', it says that light is slower in a medium when its frequency is beyond the phonon spectrum. So do lights that have frequency within that spectrum move at the speed of c, not being slowed down by the medium?
 
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  • #2
bubblewrap said:
In the FAQ section 'Do Photons Move Slower in a Solid Medium?', it says that light is slower in a medium when its frequency is beyond the phonon spectrum. So do lights that have frequency within that spectrum move at the speed of c, not being slowed down by the medium?

No. There can be several outcomes for this depending on the nature of the material. The simplest being that the light tends to be absorbed and its energy dissipated via heat, i.e the material is opaque to this light. This is because there are vibrational modes of the material that correspond to the same frequency.

Zz.
 
  • #3
Light is almost always slower than the speed of light in vacuum, also above the phonon spectrum. Especially, for light in the visible range, the interaction with electronic excitations in the ultraviolet is much more important than the interaction with phonons in the IR.
 

1. What is the definition of "light in a medium"?

Light in a medium refers to the behavior of light as it travels through a substance, such as air, water, or glass.

2. How does light travel through a medium?

Light travels through a medium in the form of electromagnetic waves, which can be absorbed, reflected, or transmitted depending on the properties of the medium.

3. What factors affect the speed of light in a medium?

The speed of light in a medium is affected by the density and composition of the medium. It also depends on the wavelength and frequency of the light.

4. How does the index of refraction affect light in a medium?

The index of refraction is a measure of how much a medium slows down the speed of light. A higher index of refraction means that light will travel slower through the medium.

5. Can light be bent or refracted in a medium?

Yes, light can be bent or refracted as it travels through a medium with a different index of refraction. This is what causes objects to appear distorted when viewed through a glass of water or a lens.

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