Is there a wave having frequency below ELF?

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Discussion Overview

The discussion revolves around the possibility of electromagnetic (EM) waves having frequencies below 1 Hz, exploring the implications of such low frequencies on wavelength and detection challenges. Participants engage in clarifying concepts related to wave properties and the feasibility of generating low-frequency EM waves.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions whether a wave with a frequency of 1 Hz could have a wavelength equal to the speed of light, leading to a clarification about the relationship between wavelength and frequency.
  • Another participant confirms that a 300,000 km long electromagnetic wave is theoretically possible, emphasizing that there are no physical rules preventing such a wave.
  • A participant expresses a desire to understand if waves with frequencies less than 1 Hz can exist, which is affirmed by others.
  • Some participants note that while EM waves with frequencies below 1 Hz can be created, the challenge lies in their detection rather than their generation.
  • One participant elaborates on the conditions under which low-frequency EM waves can be generated, mentioning the quasistatic approximation and its implications for measuring fields at small distances from the source.
  • Another participant suggests using an antenna to create low-frequency waves, indicating that higher frequencies are easier to generate.

Areas of Agreement / Disagreement

Participants generally agree that EM waves can have frequencies below 1 Hz, but there is some disagreement regarding the ease of creating versus detecting such waves. The discussion remains unresolved on the practical aspects of generating and measuring these low-frequency waves.

Contextual Notes

Limitations include the dependence on definitions of frequency and wavelength, as well as the unresolved challenges related to the detection of low-frequency EM waves compared to their generation.

vishnumanu
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speed of light = wavelength X Freq. Suppose Freq of the wave is 1 Hz, then isn't ist possible that the wavelength is equal to the speed of light? Is there anything like that?
 
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If the frequency is 1 Hz, the wavelength is ~300,000km. A wavelength is a length, and not a speed. It doesn't make sense to say "wavelength equals speed of light" because they don't measure the same thing. It's like saying "I weigh 40 miles per hour", or "I can run at a speed of 40lbs". You can't compare things that don't have the same units.

You can certainly have a 300,000km long electromagnetic wave, there's no rules in physics forbidding this. It would be an ultra-low-frequency wave for sure, but nothing theoretically prevents this.
 
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yes i actually meant was that such kind of a wave will have a 300000 km long cycle. sorry for the wrong way of expressing it. English is not my main lang.
One more question... :)
Is it also possible to have waves having frequency less than 1 hz?
 
Yes, EM waves can have a frequency less than 1 hz. They are just very difficult to create.
 
Drakkith said:
Yes, EM waves can have a frequency less than 1 hz. They are just very difficult to create.

They're easy to create; it's detection that's difficult. Hold a charged object (static electricity from stroking the cat is fine) in your hand, and then move your hand back and forth at whatever frequency you want. You're generating EM radiation at that frequency.
 
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The point is that you won't realize that you create em. waves, because you measure the field at distances from the source which is (very) small compared to the wavelength of your wave, and there the quasistatic approximation is fine, i.e., you'll measure something like a time-dependent field which behaves as an electrostatic and magnetostatic field from the ("slowly") moving source rather than something which is approximately like a (plane) wave, which you only get when going to distances from the source large compared to the wavelength.
 
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Nugatory said:
They're easy to create; it's detection that's difficult. Hold a charged object (static electricity from stroking the cat is fine) in your hand, and then move your hand back and forth at whatever frequency you want. You're generating EM radiation at that frequency.

I was thinking of trying to create them with an antenna, where the higher the frequency the easier it is to create.
 

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