Legitimacy of Particle-Wave Duality

[Zacarias Nason]

I'm asking this question not because of my own misgivings but someone else on this forum some time ago made a comment in a different context which, when talking about teaching Quantum Mechanics, was something like, "Do they still teach things like the particle-wave duality, too?" as a criticism.

I simply don't know enough about this other than a rudimentary understanding and vague relation to the De Broglie wavelength and the Photoelectric effect, and haven't run into it as a standalone topic in QM. I'd like others' thoughts on this, because as far as I am aware with my pretty limited knowledge, particle-wave duality isn't some ridiculous, fundamentally flawed concept as the poster made it out to be.

Even if it was, I still think it was a little absurd that the above was said when we still teach things like the plum pudding model as a temporary stepping stone to an electron cloud model, or we still teach the octet rule in Chemistry despite it only being valid for very limited cases; particle-wave duality could, carefully applied, be a pedagogical tool, regardless of if it is exactly true.

What is (or is not) wrong with particle-wave duality?

 

[BvU]

In my view nothing. But it seems to irritate threoreticians . I'm happy with the idea that a physics subject can be dealt with employing a certain paradigm, but that you most likely will have a deeper layer where things are (quite) a bit different and corrections for extreme situations may follow.

 

[drvrm]

I'm asking this question not because of my own misgivings but someone else on this forum some time ago made a comment in a different context which, when talking about teaching Quantum Mechanics, was something like, "Do they still teach things like the particle-wave duality, too?" as a criticism.

You are right about the questions being raised about "correctness" of the older theories working in development path of physics-evolution of perspectives.there are other examples-say Bohr's atomic model etc.

At each level the working of the 'model' as wave or at some other time as particle was substantiated by experimental observation but later developments in quantum theory did not need a description as wave or particle.
Its like working with a model and it gives you results -showing the correctness of the "model" - but one must not substitute his "model" for the actual thing.
A glaring model description is force of gravity -which we treated as force existing between masses- but now we see the effect of gravity as a curvature of "space time' in the GTR.
unless one goes tothe description of particles and their creation/interaction in terms of Quantum Field theory-the model mechanism will prevail.

 

[BvU]

We had a thread about relativistic mass, a pretty advanced subject in my view, where I got the impression the theoreticians really wanted it rooted out.

we have a FAQ on why relativistic mass is seldom used - look for a link to it in the sticky thread at the top of this forum

[edit] found it:

I am not sure exactly what E = mc^2 means.

And I have high esteem for Oro, but here we differ. (See #4, #8,#11 -- he has good points)

 

[DrChinese]

You could consider "wave-particle duality" in light of the Heisenberg Uncertainty Principle. If you do that, you will see that "wave" and "particle" are essentially the extreme points you occupy on what is actually a continuous spectrum. If you know position accurately, it acts as a particle. If you know momentum accurately, it acts as a wave. But you can also get behavior which is (very loosely speaking) half-wave and half-particle too.

So there is nothing particularly special about the duality in this light, as it maps to another quantum principle. But it is often convenient in terms of a mental model.

 

[Nugatory]

I won't speak for the other mentors and science advisors, but I tend to judge imperfect models such as wave-particle duality by the amount of grief that they cause me: The more time I have to waste spend trying to unconfuse people who have been confused by a model (usually by not understanding its limitations), the more critical of it I am. The popular presentation of "wave-particle duality" is a major offender.

 

[vanhees71]

In my view nothing. But it seems to irritate threoreticians . I'm happy with the idea that a physics subject can be dealt with employing a certain paradigm, but that you most likely will have a deeper layer where things are (quite) a bit different and corrections for extreme situations may follow.

Well, what's wrong with it is that it is an long out-dated concept. It was substituted by modern quantum theory in 1925.

 

[Zacarias Nason]

You could consider "wave-particle duality" in light of the Heisenberg Uncertainty Principle. If you do that, you will see that "wave" and "particle" are essentially the extreme points you occupy on what is actually a continuous spectrum. If you know position accurately, it acts as a particle. If you know momentum accurately, it acts as a wave. But you can also get behavior which is (very loosely speaking) half-wave and half-particle too.

This is a really, really cool concept. I've never seen it like that.