• Members 474 posts
    March 8, 2024, 12:11 a.m.

    Well, inasmuch as we "know" anything, modern physics definitely posits light as a wave. From your first article:

    The scientists shot a stream of electrons close to the nanowire, using them to image the standing wave of light. As the electrons interacted with the confined light on the nanowire, they either sped up or slowed down. Using the ultrafast microscope to image the position where this change in speed occurred, Carbone’s team could now visualize the standing wave, which acts as a fingerprint of the wave-nature of light.

    However, the article continues:

    While this phenomenon shows the wave-like nature of light, it simultaneously demonstrates its particle aspect as well. As the electrons pass close to the standing wave of light, they “hit” the light’s particles, the photons. As mentioned above, this affects their speed, making them move faster or slower. This change in speed appears as an exchange of energy “packets” (quanta) between electrons and photons. The very occurrence of these energy packets shows that the light on the nanowire behaves as a particle.

    This shows that it is the process of measurement that results in the particle notion of light. That is, while the light itself is a continuous wave, when we measure the light, we always get discrete results, and thus interpret these results as measuring "photons" of light. This is the famous Measurement Problem.

    Of course, we can get really metaphysical about all this. For example, what does it mean for something to be "real", or, more to the point, "physical"? For example, the electron, also a wave (per modern physics) but measured as a discrete particle with identical properties no matter which electron we measure, has angular momentum. However, numerous experiments performed on the size of an electron show that whatever size it has (if any) is way, way, way too small to have the amount of angular momentum that it does (else it would have to be spinning faster than the speed of light). Thus, we disassociate the angular momentum of an electron from any connection to a physical "spin".

    In the end, all we have is mathematics to describe the results of our measurements. What "reality really is", inasmuch as such a thing as "reality" even exists at all, is simply our best guess based on what we think we know at the time. After all, if you look at the history of science, one thing has always been true: what we believed to be "reality" has not only proved to eventually be wrong, but often absurdly wrong, as in, what we previously believed to be "the truth" is nothing even remotely like what we now believe to be "the truth", and it's more than a little arrogant to think that we will ever know. What may well happen, however, is we will "know" as much as we'll ever know, so that will become our understanding of "reality" from there on out. But the machines we make will be able to understand far more than us, but will not be able to explain it to us, as we will be incapable of understanding (like a human trying to explain something to an ant). But the machines will reach their limits, too, ad infinitum.

    For now, though, light is probabilistically measured as a particle as described by a deterministic wave function. That should be easy for Don to understand, anyway. 😁

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    March 8, 2024, 12:30 a.m.

    Well said. For example we quite happily view QE charts where one axis is scaled in wavelength and the other axis is based on photon capture.

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    March 8, 2024, 1:28 a.m.

    Not sure how any of that, to include anything in the Wikipedia article, is at odds with what I've said. For example, interference is incompatible with particular nature. On the other hand, we measure EM energy in discrete quanta (photons), which is at odds with a wave description, but more the domain of the Measurement Problem linked to above.

    Well, it's hard to argue with that, so I can't say I disagree! 😁

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    March 8, 2024, 6:41 a.m.

    Rather than say light is both wave and particle, I would say that light propagates as a wave and is measured as a particle. However, in the Pilot Wave model, a "guide wave" pushes a particle around, allowing one to say that light is actually a particle. So far as I'm aware, it is consistent with wave collapse upon measurement, but the wave would then necessarily need to be physical (as opposed to a probability amplitude), but not something that could be measured directly -- only measured by the particles it is pushing. Well, at the very least, no more sus than dark matter. 😉

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    March 8, 2024, 3:39 p.m.

    [deleted]

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    March 9, 2024, 7:04 a.m.

    However, the HUP (Heisenberg Uncertainty Principle) cannot explain diffraction around a barrier, because there is no finite constraint on the particle's position (e.g. light diffracting on the edge of a wall).

    Actually, it's the opposite, is it not? That is, partial reflection is an issue for the particular model of light, not the wave model.

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  • March 10, 2024, 4:05 p.m.

    One little thing: we don't know (and likely will never know), what photon actually is. All we can do is to create better and better models to describe its behavior, statements like "light traverses like wave and interacts like particle" are pretty good generalised descriptions :)

    One more link: Diffraction without Waves: Emergence of the Quantum Substructure of Light
    This includes math, what I can't grasp - I hope you can :) But conclusions are clear - first-order behavior of light is exactly wavelike, second-order not anymore.
    In everyday scenaries (like diffraction in lens) using wave theory is good enough.

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    March 10, 2024, 7:33 p.m.

    I though a photon was a fluctuation in the electromagnetic quantum field?
    (But don't ask me to explain that).