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A question about wave/particle duality

  1. Jun 12, 2018 #1
    Subatomic particles can take the form of a wave or a particle. While in wave form, it is not like a physical wave, but rather a probability wave, (i.e. a wave of information about where the particle is probably located etc.) And while in particle form, a photon, for example, can knock electrons out of atoms in a similar fashion to a coconut shy. This implies that whilst in 'particle form' a subatomic particle has a more solid aspect than whilst in 'wave form'.

    My question is: Are there particular points at which subatomic particles shift from waves to particles? Do they keep shifting to-and-fro, in the sense of manifesting as a wave then as a particle, and back to a wave again? If so, how long can they spend at each phase?

    I've read many times that only when you measure it, does a particle snap into definite existence at a particular location - but only at the point of measurement. I don't understand this. Does this imply that if a particle isn't measured let's say for an hour, then during that hour a particle must be a wave, which isn't an actual solid object? And only once it's been observed does it become the 'more solid' aspect? And at what point might it turn into a wave again?

    How can this behaviour build up the physical world, which seems to be so constantly solid?

    I know I've asked a lot of questions there, hope that's okay. I'm trying to firm up my knowledge about quantum mechanics.

    Thanks in advance,

  2. jcsd
  3. Jun 12, 2018 #2


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    This is not a very good way of describing it. The wave-particle duality is a concept that was used when quantum theory was first developed about 100 years ago. A more accurate statement is that subatomic particles are best described as quantum particles in a quantum field theory. These quantum particles have some properties that you would typically associate with a classical particle and some properties that you would typically associate with a classical wave. In other words, a quantum particle does not take the form of a classical particle or wave, it has some properties associated to those concepts and depending on how you do experiments with it either the particle or wave properties make themselves prominent.
  4. Jun 12, 2018 #3


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    Good questions. The problem with these tiny particles is, the assumptions you use in everyday life about how the physical world operates don't work. The only way to get a real grip on what is going on is with mathematical descriptions. Absent the math, wave/particle duality is a way to use familiar intuitive concepts to describe what the math is telling us. Sometimes the math tells us a photon acts like a bowling ball. Other times it tells us it acts like a wave. Those are just convenient analogies, so don't get hung up on whether a photon or an electron is a particle or a wave, or switches back and forth between those states. It doesn't. But to describe how it behaves it is convenient to imagine that it does.
  5. Jun 12, 2018 #4


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    The problem here is that you are having the classical understanding that "wave-like" behavior and "particle-like" behavior are described via two different and separate ideas or formalism. Thus, you think they have to switch from one form to the other. They don't!

    QM doesn't have to switch gears to describe each of these behaviors. If you were to learn QM first before you learned all about these waves and particles properties, you'd never be saddled with thinking that these are two separate descriptions.

    So, the only way to overcome this is for you to drop the notion that wave-like observations and particle-like observations are due to different descriptions. They need not be.

  6. Jun 12, 2018 #5


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    It seems like you have been watching too many of the “Transformers” movies. Particles don’t transform between particle or wave form.

    They are at all times quantum particles. They are not at any time classical waves nor are they ever classical particles.

    They are always quantum particles, which always exhibit behavior that you might colloquially associate with waves or particles. However, the colloquial association with waves or particles has no bearing on any part of the math or predictions.
  7. Jun 13, 2018 #6
    These are great answers. Thank you. I know where to come when I have questions about QM. Cheers
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