Why exactly do electrons emit photons?

  1. When electrons gain enough energy to move out to a higher energy orbit then back to their ground state, why do they release a photon? Also, what exactly is 'electromagnetic' about light?
     
  2. jcsd
  3. Drakkith

    Staff: Mentor

    They have to lose energy to fall back down into the lower orbitals. The only way they can do this is by releasing a photon. They are not "orbiting" the atom in the way a planet orbits a star. The exist kind of like a standing wave in which there are only certain frequencies (energy levels) that they can have.

    Light is composed of an oscillating electric and magenetic field. That is why it is electromagnetic.
     
  4. ZapperZ

    ZapperZ 29,980
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    You DO know that I don't need an electron decaying back to its lower orbital to get light, don't you? I could take an electron (or a proton or any charged particle) and jiggle it up and down, and voila! I've created electromagnetic wave/light! It isn't just a property of electrons!

    Zz.
     
  5. A photon is a quanta, a bundle, of electromagnetic radiation.....a single photon is the smallest increment of radiation......and electromagnetic radiation is a form of energy....so when a particle releases a photon it is ridding itself of some energy.....the higher energy orbital is less stable.....analogous to a pencil balanced on it's point....

    Electromagnetic waves consist of a wide range of frequencies...."light" is part of that....and different colors have different frequencies......Light refers informally to the visible portion of the spectrum....sometimes to the entire spectrum.
     
    Last edited: Jul 27, 2011
  6. Would you mind posting a link showing photons of light being produced in this manner? I am not sure I understand "jiggle". TIA.
     
  7. Drakkith

    Staff: Mentor

    Jiggle: To jiggle.

    Just like it sounds!
     
  8. the description of electromagnetic radiation is a direct result of maxwell's equations that predict electromagnetic radiation in changing magnetic and electric fields. that the EM radiation is quantized, was most simply described by the famous photoelectric effect.
     
  9. Well to be honest, I never said that you DO need an electron decaying back to its lower orbital to get light. :S That's really the only way I know how light is produced. Ok, but what actually causes an EM wave to form when you 'jiggle' an ion up and down?
     
  10. I know the electrons don't actually orbit the nucleus, ok, so do they release a photon because it's pure energy? When you say light is composed of an oscillating electric and magenetic field, what does that mean exactly? I've heard it before, but why do the fields oscillate?
     
  11. ZapperZ

    ZapperZ 29,980
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    Go to ANY synchrotron light source facility. Look up what happens when the bunches of electrons go through a series of magnets called either undulator or wiggler (the names should already give you hints on what they do to the electron bunches).

    Zz.
     
  12. Drakkith

    Staff: Mentor

    Heh, I tried writing something up right before bedtime here, but I'm so tired i couldn't even think. Maybe tomorrow!
     
  13. The acceleration of the charge in the "jiggling" process causes radiation, it's standard electrodynamics. Two of the four Maxwell equations basically say (gross simplification) "electric fields are generated from changing magnetic fields" and "magnetic fields are generated from changing electric fields". If you have a charge that is moving with constant velocity it generates a static magnetic field. But if you have a charge that is accelerating, it will cause a varying magnetic field, which in turn alters the electric field. The loop continues and a ripple in the electromagnetic field propagates away from the charge. That's a photon.


    Anyway it's far more elegant when you see it derived from the actual equations, apologies if my explanation is slightly wrong or messy.

    EDIT- 500th post!
     
  14. Great example of jiggling electrons (sounds a lot like Bremsstrahlung radiation). Do you know one for proton jiggling that does not involve electrons jumping from energy level to energy level?
     
  15. Drakkith

    Staff: Mentor

    I don't see how we have been "criticising" instead of teaching. But I guess everyone has their own views.
     
  16. ZapperZ

    ZapperZ 29,980
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    The Tevatron, the LHC, and RHIC.

    Those are either protons, or heavy ions, going around in circles, which by definition, are accelerating. The radiation they give off due to the curved path is why these circular accelerators are getting larger and larger as they need to go to higher energies.

    These may not be "jiggling", but it is the same principle.

    Zz.
     
  17. To fall down to a lower energy level, they loose energy (that cannot appear to just loose it in the case that is disappears as you cannot destroy energy, think conservation of energy) so the way to loose this energy is to release it by releasing a photon.
    Light is part of the electromagnetic spectrum as well as x-rays and game-rays, all rays you can think of, something is in the electromagnetic spectrum if it has a frequency
     
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