Why we use the direction of electric field to specify the polarization of an electromagnetic wave?
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$\begingroup$ If you mean to ask why not the magnetic field instead, that's because it's just a convention. $\endgroup$– AvantgardeCommented Oct 28, 2018 at 17:37
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$\begingroup$ @Avantgarde But I want to know why? From where this convention is coming? $\endgroup$– Pratyay RoyCommented Oct 28, 2018 at 17:40
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$\begingroup$ Historical reasons. Conventions can't be derived. It's a choice. $\endgroup$– AvantgardeCommented Oct 28, 2018 at 17:44
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$\begingroup$ Can you give me the conventional reference of this topic?😕 $\endgroup$– Pratyay RoyCommented Oct 28, 2018 at 17:46
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1$\begingroup$ en.wikipedia.org/wiki/Polarization_(waves). Search for the word "convention". I think you're reading too much into a convention. You just accept a convention and move on. If you like, you could choose your own convention, but the physical result will be the same anyway, which is why choosing a particular convention is not a point of concern. $\endgroup$– AvantgardeCommented Oct 28, 2018 at 17:50
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2 Answers
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I would suspect this is because the action of the electric field of electromagnetic waves is more significant than the action of the magnetic field (for nonrelativistic charges).
answered Oct 28, 2018 at 18:40
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1$\begingroup$ not true for antennas, both can equally be received: the E-field with a linear dipole, the H-field with a circular loop. $\endgroup$ Commented Oct 28, 2018 at 19:03
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$\begingroup$ @hyportnex: I don't see what is not true in my answer. I said that the action of electric field on a non-relativistic CHARGE is more significant, and you just need to look at the expression for the Lorentz force (en.wikipedia.org/wiki/Lorentz_force#Equation_in_cgs_units) to see that. The case where the charge is screened and the electromagnetic wave acts on the current is not relevant to my statement. $\endgroup$ Commented Oct 28, 2018 at 19:15
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1$\begingroup$ No doubt, the electric force on an electron will be more significant than the magnetic force but what action is more or less significant depends on what you need to do with the action; for a radio engineer the force does not matter, instead the induced voltage does. $\endgroup$ Commented Oct 28, 2018 at 19:19
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$\begingroup$ @hyportnex : Again, I don't see what is not true in my answer. The electric field provides higher acceleration of a non-relativistic charge. In my book, that is action. On a different note, I hold radio engineers in high respect, but I am not sure their priorities determine the contents of a physics site. $\endgroup$ Commented Oct 28, 2018 at 19:39
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The magnetic field's action (force) is a plane orthogonal to the vector used to represent the field itself. For a linear polarized propagating TEM field this, of course, is the same plane that is spanned by the propagation vector and by the E-field vector: both E and k vectors and the action of the magnetic field are in the same plane. This plane also represents the proper polarization for the wave is reflected almost perfectly by wires that are parallel with it, thus the polarization convention is to represent the polarization vector by the E-field.
answered Oct 28, 2018 at 19:14