What is an EM wave composed of?

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Discussion Overview

The discussion revolves around the composition and nature of electromagnetic (EM) waves, including the reality of electric (E) and magnetic (B) field lines, the concept of "waving," and the potential existence of electric pressure waves. Participants explore theoretical aspects, implications of Maxwell's equations, and the relationship between EM waves and mechanical waves.

Discussion Character

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

Main Points Raised

  • Some participants assert that EM waves are composed of alternating electric and magnetic field vectors, while others question the reality of these field lines, suggesting they are merely visual representations.
  • There is a discussion about whether something "waves" in an EM wave, with some arguing that no physical movement is involved in the propagation of EM waves through space.
  • Participants propose the idea of an "electric pressure wave," comparing it to air pressure waves, but there is uncertainty about the definition and context of this term.
  • Some participants argue that EM waves require a medium to propagate, referencing concepts like the virtual photon flux field or quantum vacuum, while others maintain that EM waves can exist in free space.
  • There is contention regarding the implications of Maxwell's equations, with some stating that they only describe transverse waves in free space, while others suggest that empirical observations indicate the presence of a medium affecting wave propagation.
  • Participants express confusion and challenge each other's understanding of concepts, particularly around the relationship between mechanical and electromagnetic waves.
  • Some participants emphasize the need for experimental evidence to support claims made in the discussion, indicating a desire for a more rigorous approach to the topic.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the nature of EM waves, the reality of field lines, or the existence of electric pressure waves. Multiple competing views remain, and the discussion is characterized by significant disagreement and confusion over key concepts.

Contextual Notes

Limitations include unresolved definitions of terms like "electric pressure wave," the dependence on interpretations of Maxwell's equations, and the ambiguity surrounding the concept of a medium for EM wave propagation. The discussion also reflects varying levels of understanding among participants.

EEngineer91
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Hi,

I have a few question about EM waves. What is an EM wave composed of? Are the E and B field lines real or imaginary. .. if it is an wave what is waving? (Eg water is waving in tsunami)

wouldn't a pulsating chargr produce a electric pressure wave?
 
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An EM wave is composed of alternating electric and magnetic field vectors. That is, the direction and magnitude of the electric and magnetic fields are fluctuating and changing direction over time. Note that field lines are not "real" objects but merely a way of helping us visualize the fields. They are like the contour lines that show you the elevation of terrain on a map.

wouldn't a pulsating chargr produce a electric pressure wave?

I don't know what an electric pressure wave is. An AC or pulsating DC voltage source with generate EM waves within the circuit it is connected to.
 
The lines of force are just a way of representing the fields. An EM wave is 'composed of' varying E and B fields which propagate through space or a medium. The name "wave" tells you that EM waves share a number of characteristics with other, visible mechanical waves. In the case of EM waves, nothing actually needs to wave about, though. No movement is involved with waves moving through empty space but charged particles are sometimes measurably displaced as an EM wave moves through a 'medium'.

I'm not sure what sort of "pulsating Charger" you mean but when you switch an electric current on and off, an EM pulse will radiate out into space. You may have heard 'click' interference on a radio when a heater is switched on and off and everyone will have heard the sort of interference that old car ignition systems can cause on weak radio signals.
 
So EM waves (real) are composed of things we do not consider real (E and B induction)?

An electric pressure wave is the same as an air pressure wave...a non - transverse wave
 
That's my point...they need a medium to propagate...the virtual photon flux field...or quantum vacuum
 
Of course we consider them as "real". Reality doesn't have to involve mechanical movement.
I don't know what you mean by "Electrical Pressure Wave". What is the context of that term? Are you referring to piezo electric distortion?
 
EEngineer91 said:
That's my point...they need a medium to propagate...the virtual photon flux field...or quantum vacuum
I think you need to describe your level of actual knowledge of this topic. Do you know what a virtual photon flux field is? You may just be trying to jump too far in one go.
 
Imagine an air pressure wave...now replace the air with E and B field lines...a electro pressure waave...with longiudinal propagatiion
 
Yes, I have a bachelors degree in physics thanks
 
  • #10
EEngineer91 said:
Yes, I have a bachelors degree in physics thanks

So you will know about Maxwell's equations and the solution which gives a propagating EM wave? The fields are transverse for a plane wave. In situations near a conducting structure (tied waves etc) the field may be longitudinal.
The situation with a mechanical pressure wave is very different, that can be longitudinal or transverse and it is risky to try to draw too many conclusions about EM waves from what you know about mechanical waves.

You have confused me because you have used a term "quantum vacuum" yet you seem to be wanting a very mechanical model for your EM waves.
 
  • #11
Well, maxwell equations give no longitudinal waves only in free, empty space. Empirically, space is not free or empty but prevaded by a sea of virual photons popping in and out of existence
 
  • #12
So you want an Advanced Physics discussion but using mechanical models? You can have one or the other but not both, I think.
 
  • #13
Im sorry you think those two concepts are mutually exclusive...the fact is they must be interrelated
 
  • #14
EEngineer91 said:
Imagine an air pressure wave...now replace the air with E and B field lines...a electro pressure waave...with longiudinal propagatiion

This can occur in conductors where there are charges that are able to move in response to the applied fields, but there is no such thing in free space. EM waves in free space are transverse waves.
 
  • #15
EEngineer91 said:
Well, maxwell equations give no longitudinal waves only in free, empty space. Empirically, space is not free or empty but prevaded by a sea of virual photons popping in and out of existence

So what would be changed in our understanding of EM waves if scalar longitudinal waves existed in some virtual medium?
 
  • #16
Well, our understanding would go beyond standard theory and you could produce non-linear effects. ..propagation of em waves relates to velocity of light...all this could not apply to non-transverse waves since photons are only transverse...and like I said for empty space derivation there is no such thing as free (empty) space so these derivations are a limiting and special case...you claim these field lines have no reality but em waves do...this is not consistent
 
  • #17
I can't even understand what you're trying to get at. It appears to make absolutely no sense.

Also, field lines are visual representations of what the field is doing. They allow us to visualize the force that the field will apply to charged particles. That's all they do. The wave itself does not consist of field lines.
 
  • #18
EEngineer91 said:
Well, our understanding would go beyond standard theory and you could produce non-linear effects. ..propagation of em waves relates to velocity of light...all this could not apply to non-transverse waves since photons are only transverse...and like I said for empty space derivation there is no such thing as free (empty) space so these derivations are a limiting and special case...you claim these field lines have no reality but em waves do...this is not consistent

I think it's time you provided some reference or experimental evidence for your opinion here. (It is not textbook stuff). That is what us needed for PF. Opinions are not really accepted without some backup. Read the forum rules.
 
  • #19
EEngineer91 said:
Well, our understanding would go beyond standard theory and you could produce non-linear effects. ..propagation of em waves relates to velocity of light...all this could not apply to non-transverse waves since photons are only transverse...and like I said for empty space derivation there is no such thing as free (empty) space so these derivations are a limiting and special case...you claim these field lines have no reality but em waves do...this is not consistent

So are you saying these waves could transmit information at FTL speeds or counter the laws of thermodynamics and relativity?
 
  • #20
I simply ask what is waving in an em wave...I hear its field lines but these are not real but em waves are lol
 
  • #21
Velocities would not apply to these "waves"...they are non electromagnetic...light constant is directly related to permittivity and permeability of free space...which is not empty but is considered so when doing theorectial calculations...not correct completely
 
  • #22
Personal theories are not allowed. Thread closed.
 

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