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Sorry if this a weird question here but is the electromagnetic spectrum a 'thing' (energy) or it is just a representation of the electromagnetic continuum?

For example on telecommunications, if you are referring to the electromagnetic radiation that is propagated by an antenna as a resource wouldn't it be more precise to call it like that: "electromagnetic radiation", instead of referring to the resource as "the electromagnetic spectrum"?

Further questions to clarify:

Would you consider the electromagnetic radiation propagating over a country the electromagnetic spectrum available that is located there?

Is it scientifically accurate to say that a more extended country has more electromagnetic spectrum available than a smaller country?

Wouldn't it be more accurate to say that a country has more available electromagnetic field over it instead of electromagnetic spectrum over it?

I want to know the opinion of the physicists on this matter.

Ventolinmono
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    This is question about the use of words rather than physics – mike stone Apr 19 '21 at 00:27
  • The electromagnetic spectrum is the organization and classification of electromagnetic radiation. However, the electromagnetic spectrum in the same way the free space in a room is a resource, to be carefully allocated and used. – DKNguyen Apr 19 '21 at 00:28
  • So if it's a classification it is not the natural phenomena per se, right? It's just a human way to understand it, thus a measurement? – Ventolinmono Apr 19 '21 at 00:31
  • It isn't a measurement either. It's classification of the the limited possibilities that electromagnetic radiation can take on, and it is resource because the "only one of each" can exist in any spatial area at any time so you must decide how each must be used. You can't just add more. – DKNguyen Apr 19 '21 at 00:32
  • Agree, classification is not measurement. I like the conceptualization of it as an empty space that needs to be carefully allocated and used. – Ventolinmono Apr 19 '21 at 00:34
  • I honestly don't quite grok the questions that seem to be connecting the size of a country to the extent of its electromagnetic spectrum 'located' there. The connection isn't remotely apparent to me. I suspect that you're thinking in terms of a regulatory, e.g., FCC definition of spectrum rather than a physical or physics definition. – Alfred Centauri Apr 19 '21 at 00:34
  • I'm thinking that regulators need physicists to help them manage telecommunications as geologists could help regulators manage mine concessions. In this case the way they conceptualized the electromagnetic waves or the spectrum based on updated scientific facts. – Ventolinmono Apr 19 '21 at 00:43

4 Answers4

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The entire electromagnetic spectrum is a natural phenomenon which encompasses a very broad range of things we can physically measure and study, comprising radio waves, infrared radiation, visible light, ultraviolet light, X-rays and gamma rays. It exists independently of human observation and is not a representation of something or anything else. It is a resource which can be put to use.

To make use of that resource, government organizations allocate specific segments of that spectrum for use by their citizens for specific purposes to further the interests of those citizens and those governments. Those organizations cooperate internationally to arrive at consistent regulations regarding those allocation processes and those specific purposes around the world. Examples are spectrum allocations for television, FM and AM radio, two-way communications, data transmission, radiotelescopy, and so forth. As such:

"The electromagnetic radiation propagating over a country is the electromagnetic spectrum available that is located there" is a meaningless statement.

It is not scientifically accurate to say that a more extended country has more electromagnetic spectrum available than does a smaller country.

"A country has more available electromagnetic field over it instead of electromagnetic spectrum over it" is likewise a meaningless statement.

niels nielsen
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  • Ain't a bigger country can fit more radio stations transmitting in the same frequency without interference thus having more spectrum capacity? – Ventolinmono Apr 20 '21 at 00:17
  • @Ventolinmono No, your available wavelengths does not change. "Spectrum capacity" doesn't have any meaning either. – DKNguyen Apr 20 '21 at 03:57
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main source of confusion: "the electromagnetic spectrum" = the set of all possible frequencies of "electromagnetic radiation"

For example on telecommunications, if you are referring to the electromagnetic radiation that is propagated by an antenna as a resource wouldn't it be more precise to call it like that: "electromagnetic radiation", instead of referring to the resource as "the electromagnetic spectrum"?

yes, a radio tower might produce "a spectrum of radiation" in the sense that it can generate a continuum of different frequencies (so a set of "electromagnetic radiation"), but it cannot of course make any frequency and therefore does not produce "the electromagnetic spectrum."

Would you consider the electromagnetic radiation propagating over a country the electromagnetic spectrum available that is located there?

Not really sure what you mean here.

Is it scientifically accurate to say that a more extended country has more electromagnetic spectrum available than a smaller country?

A country? Electromagnetic Radiation can be created by many different types of sources, the sun, radiotowers, electronics. I think you are misunderstanding something here.

Wouldn't it be more accurate to say that a country has more available electromagnetic field over it instead of electromagnetic spectrum over it?

"more available electromagnetic field" is not enough because you also need to specify the amount of each frequency that you have.

Steven Sagona
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  • Thank you for your clarifications. I'm a little confused when you say that radio towers "cannot make any frequency". Don't radio towers modulate amplitude, longitude and frequency of electromagnetic radiation? – Ventolinmono Apr 19 '21 at 00:56
  • @Ventolinmono, the higher the frequency the more energy. Radio towers don't have infinite energy so they cannot create infinitely high frequencies. And higher frequency radiation is extrememly dangerous because of how much energy is in it. Just read the wikipedia article on the electromagnetic spectrum if you're still confused. – Steven Sagona Apr 19 '21 at 11:41
  • Sorry but the Wikipedia article reads: "The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies." And from Britannica: "The electromagnetic spectrum comprises the span of all electromagnetic radiation and consists of many subranges, commonly referred to as portions, such as visible light or ultraviolet radiation." And someplace else literally: "The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation." So why you wrote this was the source of my confusion? – Ventolinmono Apr 19 '21 at 23:58
  • This suggests that the electromagnetic spectrum is not precise anywhere at any time so I would say that yes, that the electromagnetic spectrum is just a representation of all possible frequencies. More precisely it is is a term that refers to all types of electromagnetic radiation. So I could say that it is not a thing that exists as a whole in a certain place and time but a representation, much like the periodic table of elements in chemistry. The periodic table is a representation and not a thing in itself. – Ventolinmono Apr 20 '21 at 00:05
  • "A spectrum" is not the same as "the spectrum" – Steven Sagona Apr 20 '21 at 03:12
  • Thanks, I think this precision is very important. – Ventolinmono Apr 20 '21 at 03:20
  • Also don't forget you can upvote and "accept" answers which provide feedback/rewards for people answering questions – Steven Sagona Apr 20 '21 at 22:22
  • Yes i don't have enough reputation to upvote. I did and it says that my vote was recorded but it will not show. – Ventolinmono Apr 28 '21 at 01:00
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The electromagnetic spectrum is the organization and classification of the physical phenomena that is electromagnetic radiation. It is the finite range of electromagnetic frequencies that can exist in any one physical space. It is not a "physical thing" the same way electromagnetic radiation is. But it is still a resource in the same way the empty space in a room is a resource, even though the empty space is not a physical "thing", to be allocated and used.

Would you consider the electromagnetic radiation propagating over a country the electromagnetic spectrum available that is located there?

No, see above.

Is it scientifically accurate to say that a more extended country has more electromagnetic spectrum available than a smaller country?

No no no. A larger country has more physical area than a smaller country but not more electromagnetic spectrum. Everywhere has the same amount of electromagnetic spectrum (same range of electromagnetic frequencies which can exist) available to it.

DKNguyen
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  • Thanks. I was reading here that "the frequency spectrum for Electromagnetic (e.g light, radio, etc) is continuous and thus between any two frequencies there are an uncountable infinity of possible frequencies". So why you say there's a "finite range of electromagnetic frequencies that can exist"? Does this depends on the technology used? – Ventolinmono Apr 19 '21 at 01:06
  • @Ventolinmono Technology places limits to the range of frequencies that are useable and accessible. Technology does not have infinite resolution. Even if it did it wouldn't matter because real signals have finite bandwidths so you can't divide a continuous spectrum into an infinite number of parts. – DKNguyen Apr 19 '21 at 03:24
  • But physics also places other practical limits. I'm pretty sure there's an minimum wavelength can be based on how much energy one photon can contain. There may not be a limit on how long a wavelength can be though (i.e. many light years across). Physics also practical places limitations. Long wavelengths are very low energy, very low bandwidth, and require very big antennas. You will have trouble making an antenna big enough and staying alive long enough for it to finish transmitting/receiving. Antennas also cannot be made infinitely short. Even atoms have a cross section. – DKNguyen Apr 19 '21 at 03:24
  • Would you say that the electromagnetic spectrum in physics is like the periodic table of elements in chemistry? – Ventolinmono Apr 20 '21 at 00:11
  • @Ventolinmono No because the periodic table is just a list. Using one element in the periodic table doesn't prevent someone standing next to you from also using iron or any other element for that matter. – DKNguyen Apr 20 '21 at 01:08
  • Your first response was that "The electromagnetic spectrum is the organization and classification of the physical phenomena that is electromagnetic radiation." Isn't the periodic table also an organization and classification of chemical elements? – Ventolinmono Apr 20 '21 at 03:26
  • @Ventolinmono Yeah but the elements periodic table aren't spatially unique and the periodic table is much more formalized. – DKNguyen Apr 20 '21 at 03:29
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It's both.

Objectively speaking the electromagnetic spectrum is a thing in itself, or 'energy' as you say, but we represent it to ourself as light and colour. In this sense it is a qualia of experience. It's why Schopenhauer called the world a representation. This goes back to Kant, and perhaps earlier to Pythagoras.

Mozibur Ullah
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    If i understood well, if calling the electromagnetic field a organization or classification and thus a representation has to do with the consideration that this classification has to do more with experience and sensing of the objective? – Ventolinmono Apr 19 '21 at 01:19
  • @Ventolinmono: Yes, along those lines. – Mozibur Ullah Apr 19 '21 at 01:27