Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The Source of All Light

  1. Jul 4, 2008 #1
    I read that the source of all light/EM radiation is an electron being energized to a higher orbit, then falling back and shedding a photon. But, I also read that an antenna transmits radio by dint of the e's in the antenna being vibrated back and forth so that the electric field lines emanating from them wiggle, like shaking a rope at one end and making waves travel down the rope, and these waves, with the help of their magnetic fields, propagate through space. Is that also an instance of e's rising and then falling? Many thanks.
  2. jcsd
  3. Jul 4, 2008 #2


    User Avatar
    Gold Member

    It's a pretty primitive description but at least metaphorically accurate (the electrons don't actually rise and fall). The two descriptions (excitation/emission and electromagnetic waves) are two ways of looking at the same phenomenon.
  4. Jul 4, 2008 #3
    No, these two kinds of light emission are very different.

    Almost all the light that we normally encounter comes from "e's in the antenna being vibrated back and forth so that the electric field lines emanating from them wiggle."

    The other kind of light emission, due to rising and falling electron energy levels, is seen more rarely. Examples are lasers, neon lights, and in nature we see these emissions from stars and galaxies. The main thing about these kinds of emissions is that the color or frequency of the light is very precise, corresponding to the size of the fall in the energy level of the electron.
  5. Jul 4, 2008 #4
    Well, this tips my Universe upside down. Firstly, I don't have formal training under my belt. I'm, shall we say, PBS Nova educated. That said, I'm not sure what you mean; do you mean that most of the EM radiation we encounter - as in radio waves impacting us, etc.? And the visible light is caused by the e's falling back to a lower orbit? Many thanks for your patience.
  6. Jul 4, 2008 #5
    You could say that all light is due to redistributions of electric charges.
  7. Jul 6, 2008 #6


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Question: Is the former what is referred to as "thermal emission", resulting in a continuum spectrum?

    The latter of course, the emission due to atomic transitions, results in line spectra.
  8. Jul 6, 2008 #7
    Yes, exactly.

    No, I mean that most instances of EM radiation, including visible and radio parts of the spectrum, are the result of thermal emission, and they don't have anything to do with electrons falling into a lower orbit.

    When electrons change their energy level in an atom they produce a discrete spectrum as see here:

    Last edited by a moderator: Apr 23, 2017
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook