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Here’s a pretty weird question:

Is it possible to create light out of oscillating electric and magnetic fields? That is if I oscillate an electric field in a direction that is orthogonal to the oscillating magnetic field, will this create light?


This question is purely theoretical and hypothetical. An answer may or may not exist. But I just wanted to know whether this is even possible with our current physics or maybe physics doesn’t allow this to happen at all. I do not know what the setup would be for this assuming it’s possible.

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    $\begingroup$ Light is oscillating electrical and magnetic fields. You can not create it without generating oscillating electrical and magnetic fields. $\endgroup$ – The Photon Mar 18 '18 at 6:08
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    $\begingroup$ But you would find it difficult to generate an electrical signal to drive a conventional antenna at the required frequencies in the 100's of THz. $\endgroup$ – The Photon Mar 18 '18 at 6:09
  • $\begingroup$ @ThePhoton exactly i would need a oscillating electric and magnetic field. But as I said I don’t know the setup to create this. This is purely hypothetical. $\endgroup$ – physics2000 Mar 18 '18 at 6:10
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    $\begingroup$ Maxwell's equations make it "difficult" to create an oscillating electric field that doesn't itself produce a perpendicular oscillating magnetic field. $\endgroup$ – The Photon Mar 18 '18 at 6:18
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    $\begingroup$ If you "create" an oscillating electric field, then Maxwell's equations tells you that this coexists with an oscillating magnetic field. They are not separate things. $\endgroup$ – Rob Jeffries Mar 18 '18 at 11:43
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I think there should be an interplay between E and B field's changes in space and time. There should be a correlation between this two. The factor is not only the oscillating field but their variation (just like any normal wave equation). As you see that the potentials $\phi$ and $\bar{A}$ are just time and space component of four vector, $A^{\mu}$. So these E and B fields are the just different reflection of same four vector or same physics (Electromagnetism).

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That is if I oscillate an electric field in a direction that is orthogonal to the oscillating magnetic field, will this create light?

How a time varying electric or a magnetic field should be created?

  1. This is possible by a redistribution of charges ( applying an external electric field). The best example will be the oscillation of electrons in an antenna rod or any wire. As a result of the accelerated electrons they emit photons.

  2. Applying an external magnetic field, the involved subatomic particles get aligned with their magnetic dipole moments. During the relaxation they emit EM radiation too.

  3. Running electrons in curved paths - for example applying a magnetic field non parallel to the direction of movement, electrons will loose their kinetic energy, emit light and came to a standstill.

So however you induce an oscillating electric or magnetic field, you will influence some subatomic particles of an influenced body and follow one of the above scenarios. Or could one give different examples? The emission of light aka EM radiation is always the result of manipulation of subatomic particles. No radiation without materialistic sources.

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