If light has no charge and mass, how can it have an electric field?

  1. Since it does have an electric field, if we were to put a positive test charge near it, would it exhibit an inward field or an outward field?
     
  2. jcsd
  3. Matterwave

    Matterwave 3,859
    Science Advisor
    Gold Member

    A photon doesn't produce an electric field, it is a neutral particle as you stated in the title. Photons are the excitations of the electric field.
     
    1 person likes this.
  4. Vanadium 50

    Vanadium 50 18,034
    Staff Emeritus
    Science Advisor
    Education Advisor

    A test charge would move first in one direction, then the other.
     
  5. sophiecentaur

    sophiecentaur 13,895
    Science Advisor
    Gold Member

    And it does this, frequently, up in the ionosphere - or you wouldn't hear HF transmissions from all over the World.
     
  6. Do you know of any video or specific experiments that show this behavior? I'm really interested.
     
  7. Cthugha

    Cthugha 1,714
    Science Advisor

    "Direct measurement of light waves", E. Goulielmakis et al., Science 305, 1267 (2004). http://www.attoworld.de/Documents/papers/Science/Science305p1267_2004.pdf.

    These are not charges at rest moving back and forth, but you see a modulation in the kinetic energy/momentum of moving electrons, which is close enough, I guess.
     
  8. Drakkith

    Staff: Mentor

    Turn on a radio. It uses this exact behavior.
     
  9. Vanadium 50

    Vanadium 50 18,034
    Staff Emeritus
    Science Advisor
    Education Advisor

    Yes. It's called a "radio antenna".
     
  10. Funny, now I'm curious too... can there exist a photon without some sort of external/residual/whatever of a field? I know the e and m fields balance/cancel when traveling at c... really? And apologies, holiday weekdnd, kinda been drinking.
     
  11. Drakkith

    Staff: Mentor

    A photon is the quanta of interaction of the EM field, so no, it cannot exist without the EM field.
     
  12. Does a photon create it's own EM field, as it goes, or is that field just there?
     
  13. Drakkith

    Staff: Mentor

    To my knowledge, the field always exists.
     
Know someone interested in this topic? Share a link to this question via email, Google+, Twitter, or Facebook

Have something to add?

0
Draft saved Draft deleted