I'm not exactly sure how to phrase this question; I've been reading about wave -particle duality, its history and how it works. But it's really bothering me, whenever I watch YouTube videos about it or read about it, physicists seems to be careful to say that a wave such as light can BEHAVE like a particle but never at the same time.
What I am wondering is, whether light is a wave that only behaves like a particle at times or an actual particle. Or is an electron a particle that behaves like a wave at times or can it be an actual wave?
And also what is the actual mechanism behind it because I can't seem to find the answer or is it simply that no one knows?
There does seem to be one explanation, but I'm not sure if it's correct or that I understood it right. It states that a wave is continuous and infinite but when several waves are joined, they can form a pulse and that is a particle.
I studied maths at college level, computer science at university level and physics only in high school (UK education, for US college=high school and high school=secondary education). But I keep up with physics as a hobby, I'm quite familiar with classical Newtonian physics and know some amount of general and special relativity. I'm really only just getting into the quantum world but this is one of the first things that struck me.
Best Answer
The Trouble with Models
An honest answer is that we use models to simulate how the universe behaves, and sometimes our models just do not accurately display what something is. This is why there have been, are, and will be so many models in physics. Our models fail every so often. We try to keep the best models by updating and replacing as needed.
Light can behave as if it were a wave or as a particle, but it does not display behavior that only one model can totally explain. This is why the idea of the duality has been taken up. Both models are viewed as "equally correct," so both are applied. The most accurate way to describe light is that it acts like light, but that is not helpful.
In quantum mechanics, particles' behavior can be described by their wave functions. As the name implies, these functions often look more like waves rather than anything else. It turns out that these wave functions allow for particles to act as if they were a wave. On top of that, the situations where it acts like a wave is inexplicable if we think of electrons as hard particles. You can see this with phenomena like electron diffraction. In such cases, it is better to think of these electrons as waves.
Due to the fact that they exhibit so many wave-like and particle-like properties, we do not call them one or the other because the individual models do not account for the behavior we see well enough. Once again, our models are the sources of the confusion, and we are stuck with something that we apply two models to. We compromise and call it a duality; the electron is an electron, and we model it like a wave or a particle.
The Simple Answer
The simplest answer is that we do not really know what these things are.$^1$ We have nothing on our scale or within our experience that we can compare them to. Therefore, we use models of things we do know and carefully apply them. The particle-wave duality of these things is a by-product of the models we use to understand them.
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