Light Waves on Macroscopic Scale: Distinguishing from Matter Waves?

[chris2112]

scientists have observed light acting as waves on a macroscopic scale before the quantum characteristics of particles were discovered. My question is what sets apart the macroscopic wavelike characteristcs of light apart from other matter waves? This may be a stupid question but can the macroscopic observation of light waves just be an emergence of the probability waves of photons?

 

[BvU]

Not a stupid question. In a sense: yes. (to the second question: if there's no probability to observe a photon, you son't see it). A bit corny, I concede.
So if you can steer me in another direction, please do.

For the first question, I would say: the fact that the wavelength is in the visible range.

I don't think you should consider light as matter waves: photons have no mass.

 

[bhobba]

I don't think you should consider light as matter waves: photons have no mass.

The idea of matter waves was consigned to the dustbin of history when Dirac came up with his transformation theory at the end of 1926 (probably sooner - but certainly by then):
http://www.lajpe.org/may08/09_Carlos_Madrid.pdf

Thanks
Bill

 

[BvU]

Thanks Bill, but it seems to me that is heavy ammunition for Chris. The original question hints at a sense of wonder over the actual difference between light waves and matter waves. And I find it hard to pinpoint that without resorting to indicating rest mass as the only difference: to me that's more a microscopic difference. It doesn't help to say that you can have a kilogram of protons at rest and not a kilogram of photons.

Wave characteristics of matter behaviour popped up long after light was understood in terms of wave behaviour, and it came as a surprise that the core physical differences are virtually none. Conversely, light demonstrates particle behaviour (as in the photoelectric effect) making it even more complicated for a while.

Chris' question is at the very heart of of physics. Not current physics any more, but physics at a very peak in its development over time !

 

[chris2112]

so just to be clear, macroscopic light interference patterns, such as the airy disk or young's double slit, are just the photons quantum probability waves in action?

 

[ZapperZ]

scientists have observed light acting as waves on a macroscopic scale before the quantum characteristics of particles were discovered. My question is what sets apart the macroscopic wavelike characteristcs of light apart from other matter waves? This may be a stupid question but can the macroscopic observation of light waves just be an emergence of the probability waves of photons?

Just so you know, we don't have to switch to using the classical wave picture to account for the interference (and other wave-like behavior) of light. We can definitely describe such a feature using quantum mechanical description. The Marcella paper that I've referenced to many times is one such example of this treatment.

So no, this wave-like behavior isn't just a "macroscopic" observation, because it can be described microscopically and all the way up.

Zz.

 

[bhobba]

so just to be clear, macroscopic light interference patterns, such as the airy disk or young's double slit, are just the photons quantum probability waves in action?

At the beginner level that's the way its usually viewed.

However it isn't true because position is not an observable for photons. Explaining that at the beginner level though isn't easy:
http://arnold-neumaier.at/physfaq/topics/position.html

Unfortunately sometimes in physics its like that - what is taught at the beginner level needs to be unlearned later. Its a royal pain in the toosh for beginners that come here because we don't 'sugar' coat it.

Thanks
Bill