Is it possible to measure the general amount of electromagnetic field

[danielhaish]

We relating to an electromagnetic radiation as waves.
and in waves there is maximum point and minimum point but when there is permanent electromagnetic level there is no disorder or weave . so is it possible to measure it in blank space relative to other places

 

[Nugatory]

Yes. Just measure the force acting on a charged test particle.

 

[danielhaish]

so does it means that in case of Interference I will get higher permanent value then case of no wave at all

 

[Nugatory]

so does it means that in case of Interference I will get higher permanent value then case of no wave at all

If you're thinking of the brighter and darker regions that are observed in something like Young's double-slit experiment... The amplitude of the waves is greater in the brighter areas, smaller in the darker areas. I'm not sure what you mean by "permanent value" though... can you expand on your question?

 

[danielhaish]

in case of Interference two weaves cancelling each other because there isn't any change .for example in sea weaves the water height is getting up and down .
and you get Interference if there is two waves that when in one of them the water is in the high level in the other weave the water is in the low level so they canceling each other because the height of water is stay the same but you can still tell the difference between two weaves that canceling each other and case of no weaves at all because the height of the water will be higher in the case of two weaves then case of no weaves at all
. so i was wondering if it the same thing with electromagnetic , if it possible to tell the difference between two weaves that Interference and situation of no electromagnetic weaves at all

 

[danielhaish]

i

If you're thinking of the brighter and darker regions that are observed in something like Young's double-slit experiment... The amplitude of the waves is greater in the brighter areas, smaller in the darker areas. I'm not sure what you mean by "permanent value" though... can you expand on your question?

you see what I mean?

 

[Vanadium 50]

I'm having a hard time understanding you. Can you please write in sentences? If English isn't your first language and you are using some sort of autotranslator, it may help to give it one sentence at a time.

 

[danielhaish]

I am just saying that a weave is kind of thing that going up and down for example in sea waves the height of the water is getting higher and lower that way it calls waves. in case you have two weaves in opposite direction you get Interference , because when while weaves is incensing the height of water the other stay the same so you get permanent high of water but you can still tell weather there is weaves or not because in cases there weaves the height of water will be bigger then without any weaves. so i am asking if you can tell weather there is two electromagnetic weaves such as lights that cancelling each other or not light at all

 

[Nugatory]

so i was wondering if it the same thing with electromagnetic , if it possible to tell the difference between two weaves that Interference and situation of no electromagnetic weaves at all

With both water waves and electromagnetic waves, the amplitude of the wave is zero at the exact points of maximum destructive interference and double at the points of maximum constructive interference. (And note that in the case of water waves the water is not higher at the points of destructive interference, it‘s the same as if there were no wave, just as with electromagnetic radiation).

Thus, if we’re measuring the amplitude at one of the points of complete destructive interference and only there, we’ll measure zero amplitude and there’s no way of knowing whether it’s zero because there’s no wave or because we’re at a point where it happens to be zero. However, if we look at any nearby point we’ll find a non-zero amplitude there and we’ll know what we have.

(Be aware that this answer is based on idealized monochromatic waves and physically realizable situations will be harder to explain. We’d need a fair amount of math, and there’s no point in taking on that problem until you have a solid understanding of how ideal waves superimpose).

 

[sophiecentaur]

so i am asking if you can tell weather there is two electromagnetic weaves such as lights that cancelling each other or not light at all

Would this help?
When you are driving your car, listening to the radio. you can get peaks and troughs in reception. When you are in a trough, two waves ( say one direct from the transmitter and one reflected from a hill) can cancel out and you receive Nothing. There is no signal power reaching you where you are. Because of the effect of interference between direct and reflected waves, the power that would have turned up in the trough, turns up somewhere else in a peak so the total power from the transmitter is actually the same - just spread out non-uniformly.

 

[DaveE]

You can measure the strength of an EM field at a point; as @Nugatory said, with a "test charge" or in the real world with an antenna and some electronic instrument (of which there are several types). However, you will not know if there is an interference pattern if the only datum you have is at one point in space. The interference pattern is a distribution of EM energy through space. For example, if you measure an E-field of 2 V/m how would you know if that is from a single source and is 2 V/m everywhere, or if it is from the constructive interference of two 1 V/m sources with a nearby point at 0 V/m?

 

[sophiecentaur]

The interference pattern is a distribution of EM energy through space. For example, if you measure an E-field of 2 V/m how would you know if that is from a single source and is 2 V/m everywhere, or if it is from the constructive interference of two 1 V/m sources with a nearby point at 0 V/m?

With interference patterns, the field strength can vary a lot over short distances. The pattern between a distant source and a distant reflector will have dips every half wavelength on the line between the sources. Start at a peak and move λ/4 towards the source. The phase from the source will advance by λ/4 and from the reflection it will be delayed by λ/4. So the signals will be in anti-phase, forming a trough (works best with equal signal level of course). Moving at right angles to that line will cause no relative phase change so you will be moving along a maximum 'ridge'. In a car, the reception of VHF Radio can 'flutter' at a few Hz as you travel between troughs of a metre or two. A very recognisable phenomenon which you can point out to your (already snoring perhaps) passengers.