Is speed of em waves directly proportional to magntiude of wavelength

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Discussion Overview

The discussion revolves around the relationship between the speed of electromagnetic (EM) waves and their wavelength, particularly in the context of propagation through different media. Participants explore concepts related to the speed of light, the effects of frequency and medium on propagation, and the implications of dispersion.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that speed is directly proportional to wavelength in a medium, questioning whether gamma rays are slower in air compared to other EM waves.
  • Others argue that the speed of EM waves is a constant, particularly in a vacuum, and that the wave model for light indicates gamma rays can be slower in certain media.
  • There is a discussion about the distinction between propagation and existence, with one participant suggesting that they are not the same.
  • Some participants emphasize that the speed of propagation through a medium is dependent on frequency, noting that this relationship is not linear and varies with different wavelengths.
  • One participant mentions the concept of dispersion, explaining how it leads to phenomena like light splitting through a prism, and how the refractive index affects different frequencies differently.
  • Another participant highlights that while gamma rays have a refractive index close to 1 in air, lower frequencies experience a greater impact, leading to different propagation behaviors.
  • There is a mention of how gamma rays interact with solid objects differently than visible light, with gamma rays passing through prisms with minimal modification.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between speed, wavelength, and medium, indicating that multiple competing perspectives remain. The discussion does not reach a consensus on these points.

Contextual Notes

The discussion includes assumptions about the nature of propagation and the effects of different media on EM waves, which are not fully resolved. The complexity of the relationship between frequency and speed in various contexts is acknowledged but not definitively clarified.

sgstudent
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I read that speed is directly proportional to wavelength in a medium. so does it mean that gamma is the slowest in air compared to the rest of the waves?
 
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Not really. The speed of em waves is a constant.

But you are thinking in terms of propagation through a medium, using the wave model for light and you'd be correct - gamma waves are slower than, say, any visible light waves. Also means they bend the most at interfaces.
 
Last edited:
Oh okay thanks for the help! But isn't propagation the same as just existing?
 
I think what Simon Bridge is saying is that the speed of propagation through a medium is dependent on frequency, with emphasis on "through a medium".

The ratio of the speed of light in a vacuum to the speed of propagation through a medium is the index of refraction for that medium. The fact that it is different for different frequencies is known as dispersion, and gives rise to effects like the splitting of light through a prism.
 
@Jasso: that's exactly what I'm saying - thanks.

Of course it is possible to exist and not propagate... that's what birth-control is for.
 
Jasso said:
I think what Simon Bridge is saying is that the speed of propagation through a medium is dependent on frequency, with emphasis on "through a medium".
That is right, but the dependence is complicated and no where near "linear". In good approximation, all wavelengths have the speed of c in air, which is the same as they have in a vaccum.

Now, the influence of air on gamma rays is quite small (refractive index a bit smaller, but close to 1), whereas smaller frequencies get a bigger impact (and a refractive index larger than 1).
The group velocity is a bit different, but this should be a bit larger for gamma rays as well.

In solid objects, the difference in the refractive index is easier to see: Gamma rays pass through prisms without a significant modification, while visible light changes its direction.
 

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