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I'm trying to understand quantum physics. I'm pretty familiar with it but I can't decide what counts as observing to cause particle behave (at least when it's about lights). So the question is what do we see with our eye-balls?

  1. We point a laser (or any kind of light source) to the wall. We see its way from point A to B. Do I "see" a particle or a wave?

  2. Let's see an average object. It pretty much looks like their "pieces" a observing that influences their behave. Does this means while we're watching a light it acts like particle in quantum level?

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    $\begingroup$ Isn't it just the energy in light rays that gets detected by our eyes? $\endgroup$ Nov 22, 2014 at 17:15
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    $\begingroup$ The answer is "yes". $\endgroup$
    – Hot Licks
    Nov 22, 2014 at 23:02
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    $\begingroup$ "We see its way from point A to B" -- We see light reflecting off dust particles in the air. In a vacuum you would not see anything along the path. $\endgroup$ Nov 23, 2014 at 7:22
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    $\begingroup$ One needs to remember that "waves" and "particles" are just terms we humans must use to "visualize" concepts that our poor brains cannot otherwise comprehend. $\endgroup$
    – Hot Licks
    Nov 23, 2014 at 15:27
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    $\begingroup$ We can't "see" particles or waves literally. The sensation of "seeing" is the perception of phenomena and objects by the light they emit or reflect. Light is only a medium of perception regardles of its characterisation as wave or particle. This does not answer your question, I know. $\endgroup$
    – Ariser
    Nov 23, 2014 at 21:16

5 Answers 5

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You are seeing particles. However there's more to this than meets the eye so I need to explain exactly what I mean by this.

Light is neither a particle nor a wave. Instead it is a quantum field. As a general rule while light is travelling it appears as a wave, but when the light quantum field is exchanging energy with anything it does so in quanta that appear as particles i.e. photons.

You see because light excites electrons in rhodopsin molecules in the cells in your retina. Since this is an energy exchange (from the quantum field to the rhodopsin molecule) the interaction looks like absorption of a photon.

So you are seeing particles.

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It would be physically impossible to be able to "see" light as anything other than a particle (photon). The only time photons, or any other subatomic particle for that matter, can be described as a wave is when we are NOT looking at them.

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This is misconception that light is some kind of 'mix' of waves and particles. Instead, It actually IS both waves and particles at the same time, you can't separate them from each other. So probably, the answer could be: you see particles as well as waves.

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  • $\begingroup$ So you disagree with what @John Rennie said in his answer: "Light is neither a particle nor a wave. Instead it is a quantum field". Can you provide some arguments for your case? (I'm genuinely interested) $\endgroup$
    – Marc.2377
    Apr 16, 2017 at 18:42
  • $\begingroup$ A traveling “quanta” of light is associated with an electromagnetic wave packet of finite size which can produce a (probability) interference pattern measurable in centimeters or more. But, as John Rennie points out, in the eye all of it energy is absorbed by a single molecule. $\endgroup$
    – R.W. Bird
    Apr 5, 2021 at 15:28
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Light is a quantum level effect. The worst thing that science ever did, was call these things particles. The Greeks proved a long time ago, that the smallest particle in existence is the atom, which is true. That is not because the Greeks didn't know light, or didn't understand there had to be a way to get smaller, but because they understood that below the level of an atom, the understanding of the phenomena of existence changes.

Sub atomic particles do not exist as such. You and I do exist, because we can persistently express that existence in a moment we call 'now'. Sub atomic particles don't have a 'now'. Not only don't they have a 'now', some don't really have a 'here' either. An electron is actually just a charge, which is more or less said to be 'located' wherever that charge is most likely to be found if anyone could ever find it. A similar thing goes for photons. First of all, they don't exist until you destroy them and secondly, they are not really all that local.

So how can light be a particle as well as a wave? Because that's the names we gave it. In truth it's neither the one nor the other. It's an effect. It's not a thingy, it's not a substance, it's something happening that just so happens to occur in integer values and it can travel at an insane speed we call the speed of light, which is located at the far end of going fast. Not the far end of getting there fast mind you, because that's a whole different matter. Subject,... sorry. Its a subject,... different subject. Its not matter.

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What do we see with our eyeballs?

As one commenter has replied, what you see is neither particles or waves, but the qualia of light, that is colour - whether that be green, red, orange or just white.

Ontology is complex and is not just one thing and it is scale dependent. For example, in the situations you have described, classical physics is sufficient.

It's only when we probe the fine structure of reality that the classical ontology breaks down, but in no sense is this 'seen'. This, despite the fact we call measurements, for thats what they are, observables.

One of the main interpretative challenges for quantum mechanics is finding a language that does justice to its complex ontology.

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