# EM waves

Discussion in 'General Electronics Chat' started by cssc, Nov 12, 2014.

1. ### cssc Thread Starter New Member

Oct 19, 2014
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Does temperature effect the frequency, amplitude, or any other parameters of electro magnetic waves ????

2. ### kubeek Expert

Sep 20, 2005
5,585
1,094
Temperature of what exactly? Air? Vacuum? Transmitter?

3. ### cssc Thread Starter New Member

Oct 19, 2014
26
1
The medium in which its propogating

4. ### Kermit2 AAC Fanatic!

Feb 5, 2010
4,158
1,125
ordinary temp should not. at higher temp where plasma forms then yes.
in vacuum at ridicuolously high temps? i can say for sure I don't know. i wouldn't think it matters but not an accomplished math person and Maxwell and Albert E. can get over my head pretty quick when the equations on the pages outnumber english words.

5. ### kubeek Expert

Sep 20, 2005
5,585
1,094
Temperature will likely affect attenuation - as the density changes with temperature the attenutation should change as well.

6. ### alfacliff Well-Known Member

Dec 13, 2013
2,449
432
there are no tempratures mentioned in any of the formulas for propagation, and once an em wave is produced, the only thing that affects the frequency is doppler.

Last edited: Nov 12, 2014
7. ### wayneh Expert

Sep 9, 2010
16,102
6,219
I don't believe the temperature (velocity) of the mass nearby affects the speed of light passing by it. As someone noted here not long ago, there's no temperature without mass. Kobeek is correct that the density of mass will affect transmission, but the movement of that mass is not relevant.

8. ### crutschow Expert

Mar 14, 2008
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A vacuum has no temperature, which is a property of matter.

9. ### BobTPH Senior Member

Jun 5, 2013
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540
Don't see how it can. Temperature depends on the motion of molecules. According to special relativity, the speed of light will be the same relative to all of the moving molecules, so it cannot see any difference depending on their motion.

Bob

10. ### studiot AAC Fanatic!

Nov 9, 2007
5,003
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EM waves require no medium for propagation. That is what makes them different from all other waves.

Having said that they can and do travel through various media, which can be affected by temperature in several ways.
It rather depends upon what you mean by EM waves. Different parts of the spectrum are affected differently.

Basically, air temperature affects humidity and refractive index. So EM waves travelling in air can be deflected by air mass interfaces, where the air masses are at different temperatures.
Also for precise geodetic work, using EDM equipment, the manufacturers issue correction formulae and tables.

Finally the transmission (attenuation) coefficient is slightly affected by temperature.

Last edited: Nov 12, 2014
11. ### Alec_t Expert

Sep 17, 2013
10,267
2,511
The velocity of EM waves is a function of the permittivity of the propagation medium. Permittivity is temperature dependent. Ergo, EM wave velocity other than in a vacuum is temperature dependent.

12. ### alfacliff Well-Known Member

Dec 13, 2013
2,449
432
since light can be accused of being an emwave, does it change velocity with temprature?

13. ### wayneh Expert

Sep 9, 2010
16,102
6,219
Temperature affects how light interacts with the mass it is passing through, because it changes the properties of the mass, not the light. Light and mass interact when the mass can accept a quanta of energy from the light, slowing it.

This is an interesting, related study.