Speeds of Light and Electrons
Most recent answer: 08/06/2013
- Terry (age 49)
Salinas, Ca, USA
We agree that a change of an electron's state is a common source of light. I'm mystified by the idea that then "it [would] stand to reason that the electrons would have to be moving faster than the emitted photon". Why? Motions in your throat and mouth are a common source of sound. Does your tongue then have to travel faster than sound?
Mike W.
(published on 08/06/2013)
Follow-Up #1: movement of light sources
- Terry (age 49)
california
Your question remains a mystery to me. Almost any wave you wish to think of (water waves, waves down a violin string, ...) can be triggered by motions that are slower than the wave speed. Yes, that includes sound waves from either the vocal chords or from the tongue.
Ok, so let's look at electromagnetic waves like light. Instead of visible light, let's think of low frequency EM waves traveling at exactly the same speed as light, following exactly the same wave equation, but with an easier source to picture. This EM radiation can come from an antenna- just a wire in which electrons flow back and forth. The intensity of the wave grows as those electrical currents get bigger (faster electron motions), but the wave speed doesn't change. The speed of the wave remains exactly the same no matter how slowly the electrons flow back and forth.
You don't need to even think about photons to understand this. It's all in Maxwell's equations for classical electromagnetism.
(How fast might the electrons flow in a typical case? Say you've got some standard ac current, e.g. 1 amp, flowing in a copper wire with about a square millimeter cross section.The average velocity of the electrons is only around 10-2 cm/s, quite slow. )
You use the phrase "stands to reason" but you haven't explained what sort of reasoning goes against the actual content of all our physical theories.
Mike W.
(published on 08/06/2013)