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When I go through Electroencephalography,

Band    Frequency (Hz)
Delta   < 4
Theta   ≥ 4 and < 8
Alpha   ≥ 8 and < 14
Beta    ≥ 14

How much are wave length of brain wave?

Thanks for Bryan Krause's comment,"Brain waves" aren't EM waves,but mechanical wave has width as we known.

And it's obvious brain wave is some kinds of wave, with frequency and scale.

When someone is awake, with his eyes closed, the EEG is dominated by the α (alpha) band. This type of waves is characterized by a frequency of 8-13 Hz and a normal width <50 microvolts (µV).

If the subject opens his eyes, α waves disappear and another wave type becomes evident: the β (beta) type. These brainwaves have a higher frequency (30-35 Hz) and a width of 25-30 µV.

Then I still want to know Does brain wave has wave length?.

representations of different brain wave bands

Chris Rogers
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kittygirl
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    Does this answer your question? Are brain waves electromagnetic waves? – Bryan Krause Feb 17 '21 at 03:52
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    "Brain waves" aren't EM waves, see attached duplicate. The frequencies are in Hz which is units of 1/s. So you could say the length (as in duration) of a 4 Hz brain wave is .25 seconds, but that's just another way of describing the frequency. There is no length in space like an EM wave. – Bryan Krause Feb 17 '21 at 03:55
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    @BryanKrause,aren't EM waves.Can we say brain waves are waves with wave width? – kittygirl Feb 17 '21 at 07:26
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    At this present moment your question is not clear to me. At the beginning of your question you listed the wavelength frequency ranges for each type of brain wave then you seem to be asking what the wavelengths are for the brain waves? – Chris Rogers Feb 17 '21 at 10:03
  • @BryanKrause while I'm not a neuroscientist, my background is physics. In my understanding, in a purely physical point of view brain wave is EM wave. However, it seems to me that neuroscientists and physicists define EM wave differently. That lead to the confusion, because one can find one source says it's EM, then another source say it's not. I elaborate this in this answer. Hope to have my understanding corrected. – Ooker Feb 17 '21 at 13:09
  • @kittygirl did you mean "how long are brainwaves in one period?" In my understanding, we can apply the formula "length = velocity / frequency". In this case, the velocity is c, i.e. light velocity – Ooker Feb 17 '21 at 13:16
  • @Ooker The thing people call brain waves is not an EM wave. It's a time-varying voltage. I recommend AliceD's answer on the linked post. That doesn't mean the brain isn't also producing EM, just that brain waves are not it. – Bryan Krause Feb 17 '21 at 13:46
  • @kittygirl Width of what units? Time? Something else? – Bryan Krause Feb 17 '21 at 13:47
  • @BryanKrause,width is something like 20m,400cm. – kittygirl Feb 17 '21 at 20:49
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    @kittygirl There is no length (or width or anything else) in space, as I wrote in a comment above. The axes are voltage and time. The "waviness" at different frequency is because the signals in those plots are filtered to include only certain frequencies, so the "width" of a wave takes more or less time. Brain waves are not EM waves. – Bryan Krause Feb 17 '21 at 21:01
  • All waves have wavelengths. However, the unit of measure for wavelengths is not always in space (ie, it is not always in meters). As you can see from the graphs included in the question itself, the length for brainwaves is in time (seconds), which you can calculate using s = 1/Hz, as @BryanKrause exampled above. Other examples of waves with time-based wavelengths include heatwaves, ECG (heart beats), and economic cycles. Closing this question as answered in comments. – Arnon Weinberg Feb 20 '21 at 03:56
  • When someone is awake, with his eyes closed, the EEG is dominated by the α (alpha) band. This type of waves is characterized by a frequency of 8-13 Hz and a normal width <50 microvolts (μV). https://inbrain.tech/a-journey-into-the-nervous-system-brainwaves/1241/ – WhiteGirl Feb 21 '21 at 03:28
  • @ close-voters - I find it a bit harsh to close this question. I was actually planning on answering it. Pointing out that wavelength doesn't apply is a valid answer to a valid question imho. Furthermore, the fact that the synchronous firing behavior is restricted to certain local areas of the brain may actually give an idea of the wavelength, although I'm uncertain if normal physiological waves actually progress unidirectionally through cortical areas like those so characteristic of epileptical activity - have to do research on that. I was too busy to jump in. – AliceD Feb 21 '21 at 20:32
  • @AliceD I'd be really worried about answers that don't do enough to dispell this idea that brain waves are EM waves, including the sorts of answers on that linked question that argue that changing voltages must involve EM waves. Anyways, my vote to close was really only because I think this question has a dupe that already has some good (and bad) answers about what brain waves are. – Bryan Krause Feb 21 '21 at 21:13
  • @ArnonWeinberg No wavelength is measured in relation to space are they? All wavelengths (radio waves, heat waves, sound waves... and brain waves) are in units of Hertz which is cycles per second. Brain waves are different as they are not constant, hence the frequency ranges mentioned in the question. – Chris Rogers Feb 22 '21 at 08:51
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    @ChrisRogers From Wikipedia: "wavelength is inversely proportional to frequency". So WL = 1/f, or in units, m or s = 1/Hz. – Arnon Weinberg Feb 22 '21 at 18:41
  • Ah yes @ArnonWeinberg. I got confused between wavelengths and frequency. Was a while since I studied it in school – Chris Rogers Feb 22 '21 at 18:52

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