How can light interact with atoms?

DrClaude

Or the long wavelength approximation!

Indeed, I think it is much more fruitful to think about the interaction in terms of frequency instead of wavelength. Consider that the atom is embedded in a uniform electric field which oscillates at frequencies that are commensurate to the typical timescales of electron motion (in a classical picture).

NemoReally

Might it be helpful to consider that the conventional image of radio waves extends physically along the antenna, whereas the "waves" (which are better described as a bunch of phase-synchronized photons) are longitudinal? The "wavelength" isn't so much describing the physical length or extension of a photon but the distance (or time) in (our) space over which its E-M field "rotates".

What I found interesting was, taking a 10 MHz, 100 W tx, calculating how few photons pass through a half-wavelength antenna at 100 km in the duration of 1 cycle.

.............


I've used myself as an antenna on several occasions ... mostly for receive, but never at more than a few watts from the transmitter! Of course, I find I can shield myself from the CIA transmissions by using my tin-foil hat ... the Voices give good advice, occasionally.

ZapperZ

Actually, you didn't apply any logic. Your assertion that something smaller than the wavelength cannot interact with that wave is NOT based on logic. You cannot derive that from First Principles.

And considering that we have numerous experimental evidence to contradict that implies that your "logic" is faulty.

Note also that in metamaterials that have been shown to produce left-handed waves and cloaking, the structures that were built HAVE to be smaller than the wavelength of the incoming light. Now that light "sees" the structure as being "continuous" because the wavelength is longer than the size of the individual split rings and rods. However, the electrons in those structures certain DO interact with that light in such a way that it produced the necessary effects!

There is also something that you should try and learn here in this forum. When you think of something, you cannot solely rely on "logic", especially when it really isn't logical. This is science, or physics in particular. You cannot simply insulate yourself from experimental evidence and observation! So when you ask a question such as this, figure out FIRST if there are experimental evidence that contradict what you think you understand! Remember that just ONE valid experimental evidence is sufficient to falsify your "logic".

So when you think you have found that, based on some logic, light cannot interact with atoms, look for experimental evidence! Did Compton scattering never occur, for example?

Zz.

Menaus

You seem to misunderstand me. Why engage in a petty argument when you don't even understand what I'm trying to say? In fact, if you believe me to be so illogical why start such an argument in the first place? It would only end in stupidity if what you say is true.

My assertion was that something 1/5000th of the wavelength cannot interact with said EM wave, and that is accepted under experimental evidence, unless we use the aforementioned method (of making the atom look electrically 'bigger').

ZzzZzzZ

chill_factor

nope think of it this way: the wave is moving by *very fast*. that means it is oscillating at a high frequency. You should think about atoms or solids being embedded in an oscillating electromagnetic field. Don't worry about the wavelength. Microscopically things just don't obey the rules that macroscopic things do.

just an example: if what you said was true how could LEDs work when the light emitting layer is thinner than the wavelength by far? How could gas lasers work when the lasing medium is individual atoms or molecules, and an atom is emitting a wave with wavelength 5000 times bigger than itself?

Indeed it would be even more useful to think about light as pointlike photons with characteristic energies relating to their frequencies when dealing with the optical properties of materials as that can explain, and let you do, ALOT more things, than the wave picture, but even just thinking in terms of oscillating electric fields is much more useful than thinking about their wavelengths.

Menaus

http://iopscience.iop.org/0038-5670/26/10/A04

http://ajp.aapt.org/resource/1/ajpia...sAuthorized=no

Hmmm, looks like my random idea was correct.

Anyway, I'm pretty much done with this thread, there's no point in talking to people who refuse to look at my own words. I mean, before I accepted your answer, but now I can use both because they're both correct.