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Converting energy

  1. Jan 15, 2007 #1
    about a year ago i have asked how light bulbs work, the tungsten one. i was satisfied with the answer but not anymore. In brief (to make sure I have a proper understanding): as the electron moves from the higher to the lower end of wire in terms of electric potential, it releases energy. The energy is absorbed by the electrons in the atoms of the wire. The electrons jump when gaining energy and, being unstable, fall back to the original orbit, releasing photon in the process.

    My question is now, simply, are the electrons in the power source energized as they have a high volt? volt itself is described as energy/charge. Thus I interpreted the energy to be inform of photon and thus there would be either abundant amout of photon around the electrons in the power source, or just the same number of photons with higher frequency or both or am I simply wrong? Then, is the electical energy and the light is both in the form of photon?

    Thanks in advance.
  2. jcsd
  3. Jan 15, 2007 #2


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    Who gave you THAT answer?

    Let's work our way backwards, shall we?

    1. Light is produced by a heated tungsten. So heating this element is the key thing in producing light.

    2. So how do you heat it? In this case, it is via electricity, since the element has a high resistance. This is very straightforward.

    3. So what you are left with is trying to find a description at the microscopic level, which isn't what you described above. When you apply a potential difference across the ends of a wire, the conduction electron will be agitated and move faster, on average. They will bump into each other and the ions of the metal not only with a high average energy, but also more often.

    4. Such collisions will increase the average kinetic energy of the electron gas and the ions. This results in the ions vibrating more, and thus, increases the temperature of the metal.

    5. At some point, the vibrational energy is high enough that it will emit light. Since this is a vibration of a large chain of ions in 3-dimensional lattice, the vibrational spectrum is wide and practically continuous. That is why when you look at the light being emitted from a tungsten light bulb through a spectrometer, the spectrum is continuous, unlike light from an atomic gas.

  4. Jan 21, 2007 #3
    ups... it seems that i had a major misunderstanding. then how to relate this with the concept of photon as light?

    What i currently understood is that the photon is emitted by the atoms like in the reverse of photo electric effect. and the photon came from the electron.....
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