# What does it mean by a particle is a wave

1. Jun 30, 2010

### im_chc

What does it mean by a particle is a "wave"

Hi everyone, I'm not even a science student, I'm just interested in Physics
I've read a lot of Physics books... but I still can't understand what does it mean by a particle behaving like a wave.

Well, I know that it is some kind of random or statistical, there's a wave function (Shroedinger) that can predict statistically the location of a particle...

At first I thought the particle is like moving in a Sine Wave, and that the particle is still a little ball... that was my first naive understanding (".. so, this is wave-particle duality, the particle is still a ball, and at the same time it is moving like a wave, that makes sense") (!?)

Then, I realize that it is not what I know, after reading the double-slit experiment

So, can somebody explain intuitively how it is like, I think it is not easy coz AFAIK what is actually happening "physically" in a wave-function is still left to many different interpretation (from Wikipedia, Wave-function page)

Is it like a sound wave-packet moving forward? but the wave packet is not made up with one particle, but by a media (air)?

also, I read somewhere that a theory states that a particle is actually a wave propagating/occupying an infinite range of space? (but of course have a limited area of most probable location)

I'm quite dis-oriented so please excuse me, and excuse me of asking such an entry-level question, thx

2. Jun 30, 2010

### cragar

Re: What does it mean by a particle is a "wave"

People thought electrons were particles at first , but then they shot electron through a double slit and got a diffraction pattern just like light , so electrons have a wavelength
, and they have a frequency so maybe you could think of them as vibrating . Maybe look up de-broglie hypothesis . He thought if light behaves as a wave and a particle that maybe matter does the same . its kind of a tricky question to answer , hopefully someone can give a better answer ,

3. Jul 3, 2010

### AJ Bentley

Re: What does it mean by a particle is a "wave"

This isn't an entry level question.

It literally isn't humanly possible to understand the wave particle duality in the way that you might understand the workings of the internal combustion engine.

You see, At our ordinary level we just are not used to how things at the submicroscopic level work. To us things are 'things'. You put something down and it stays there. Your keys don't mysteriously 'leak' from the hall into the closet or the basement. Your toothbrush doesn't somehow fill the entire bathroom. It doesn't make sense to us that something could. But they do.

The only way you can get a handle on it is to cling to the mathematics that describe what's going on - that and a few carefully selected mental models to help you visualise some aspects of behaviour that those models happen to parallel. But bearing in mind that under slightly different circumstances that particular model is complete nonsense.

Most QM situations are best described as being a bit like radio waves moving inside a metal box and bouncing off the sides. Or sound if you prefer - the fact that they are completely different types of wave makes no difference - it's only a model you see...

4. Feb 9, 2011

### Oscur

Re: What does it mean by a particle is a "wave"

You've clearly never lost your keys. :p But seriously, you're on the money. A good explanation of the double-slit experiment, which really helped my comprehension of this phenomenon can by found in Feynman's book Six Easy Pieces. He also had http://www.youtube.com/watch?v=wMFPe-DwULM" to say about the difficulties of explaining alien concepts like quantum mechanics to non-science students.

I have to say, it's quite heartening to hear of someone who doesn't actively pursue studies in physics, but still takes an interest. We need more of them.

Last edited by a moderator: Apr 25, 2017
5. Feb 10, 2011

### Openeye

Re: What does it mean by a particle is a "wave"

so an electron isn't even a particle?

how can it be called a fundamental particle then?

are we talking about two different 'religions' (for lack of a better word) of physics here? two different ways to believe something, I mean... and that is why they are both simultaneously 'true' ?

In the thread (that I WONT link to this time, because the entire topic/thread got deleted just cause I linked to it! Also, I was warned for it :P )... just before it was closed someone was telling me that an electron is a fundamental particle based on an obvious (POSSIBLY logical) assumption. Wikipedia says it is too. But I don't like assumptions that's why I'm coming to science/physics forums to ask people, cause I think people here too might not like to just assume things as much as possible.

Here you're saying something different... and it doesn't sound like it's based on much of an assumption. I'm interested.

Thanks :)

6. Feb 10, 2011

### Drakkith

Staff Emeritus
Re: What does it mean by a particle is a "wave"

Like it was said above, the way things work at the atomic level and smaller will NOT make sense to most people. All matter, as far as we can tell, behaves like a particle AND like a wave depending on how you are observing it. Are they particles? Are they waves? They ACT like both, therefor we say they have a wave-particle duality.

Take the photoelectic effect for example. In this effect photons strike a metal plate and eject electrons from it. The energy of the ejected electrons depends directly on the frequency of the light, not the intensity. Under a certain frequency the light simply doesn't have enough energy PER PHOTON to cause any electrons to be ejected, and simply increasing the intensity (amount of light) will do nothing. This is completely opposite of what one would expect if light was ONLY a wave. This shows that energy is only transferred in specific amounts called Quanta.

Then look at the double slit experiment. In this case we can see that the photons acts like waves and interfere, causing a diffraction pattern. This would NOT be the case if light was composed ONLY of particles.

So with two different experiments we can see that light acts as both a particle and a wave depending on what you are observing about it. This also applies to matter as well. All matter acts as both a particle and a wave.

This brings up an interesting point. If it ACTS like both, what is it REALLY? Currently the only thing we can say is that it IS both.

7. Feb 10, 2011

### Openeye

Re: What does it mean by a particle is a "wave"

cool,
thanks for your answers... this is clearing a lot of things up believe it or not...

a few more things...

Are waves themselves considered PHYSICAL? (like I am assuming particles are considered)
Or would we classify them perhaps as non-physical properties of physical?

Or do we say that since a particle is both a wave and a particle (or rather, everything is)... that everything is both made up of physical and nonphysical at the same time?

And technically would waves would be more fundamental/elementary than particles?... for example... if we think about the beginning of -everything-... from the smallest 'nothing' that exploded into 'everything' (according to big bang theory right?) ... do we start as 'waves' (smallest... I know probably not the right term but do you konw what I'm saying). .. and become particles?

Or am I asking the chicken and the egg question?

8. Feb 10, 2011

### Drakkith

Staff Emeritus
Re: What does it mean by a particle is a "wave"

That's one of the things that is so hard to understand! It isn't that one or the other is physical and the other isnt. BOTH are physical and BOTH are just as real as the other.

Most people think of a wave like they would a wave on the water or the air. This is NOT what a wave is in this concept. In water or air a wave is a result of the collective motion of LOTS of air/water molecules. A wave in a subatomic concept is NOT this. It is only a way of explaining the effects we observe in a way that we can relate to.

Take the diffraction pattern from the double slit experiment. The reason we say that things act like a wave is that a classic wave, one in water or air, makes those same patterns under similar circumstances. Also, certain observations show that they only make sense using similar math to a classic wave, like frequency and such.

Make a little more sense?

9. Feb 10, 2011

### Openeye

Re: What does it mean by a particle is a "wave"

Yes... a LOT more sense! That's what I have come to know in -completely- different ways... :D

Wow... that is so not difficult to understand... what was difficult for me is the word elementary and fundamental. Doesn't feel like to me, we can ever really use those words accurately until we find a 'beginning'... (but I am extremely picky about the accuracy of communication/language... regardless of the language). But I can understand, that if someone believes they will eventually find a 'beginning' or 'starting point'... why they'd assume the smallest/finest they currently observe to be 'fundamental' until proven otherwise.

based on what I just said, does it feel like I've missed something?

Thank you for your patience with me and my lack of desire to go through everything to EVENTUALLY reach this understanding. I knew we could be more direct than I was approaching it... but I didn't know how to... :D

10. Feb 10, 2011

### Drakkith

Staff Emeritus
Re: What does it mean by a particle is a "wave"

I think that was what we were trying to get you to understand in the other thread lol. Saying something is fundamental or elementary is NOT saying that it is impossible for it to be made up of something else. It's just what we show currently. =)

11. Feb 10, 2011

### Openeye

Re: What does it mean by a particle is a "wave"

Thanks so much... (to you and the others)

"Waves" makes this make sense... but I didn't want to go there yet.

I've got lots of work to do! :D
I was stuck... but now I know exactly what to do!

"love love...love love love.... *trails off*"
(heartbreak kid movie reference)

12. Feb 10, 2011

### Openeye

Re: What does it mean by a particle is a "wave"

agh...

particles are physical
waves are physical

we (science) says waves are physical because particles show us ?

(and perhaps vice-versa?)

Last edited by a moderator: Sep 25, 2014
13. Feb 10, 2011

### Drakkith

Staff Emeritus
Re: What does it mean by a particle is a "wave"

The video shows the physical result of classical waves. The vibrations of the platform cause the salt to take different patterns, generally more complicated as the frequency increases. Again, this isn't like the particle-wave duality thing.

Last edited by a moderator: Sep 25, 2014
14. Feb 11, 2011

### LostConjugate

Re: What does it mean by a particle is a "wave"

Particle means that we can only detect it in one place in space. It is just a word we made up for the way something interacts with a measuring device.

It has wave properties, and has particle like properties when interacting with a measuring device.

It has also been proven that this is not a limitation of our measuring devices.

Perhaps it is only a limitation of thinking classically about physics.

15. Feb 11, 2011

### Quickless

Re: What does it mean by a particle is a "wave"

1. Need to think of things as existing in or as part of a field and not in isolation.
2. Particle or wave are different states of that which is being observed in relationship to the field.
3. Somewhat like water can be a solid, gas, or liquid. Which is it?

Best to think of all of this as an interesting way to engage your thoughts.

16. Feb 12, 2011

### Openeye

Re: What does it mean by a particle is a "wave"

Thank you all. :)

but now I am having more... :D

"2. Particle or wave are different states of that which is being observed in relationship to the field."

once again, I did ask it but I didn't make any connection to the responses I got so I'll ask again...

Is the way in which we observe fields, reliant on the existence/observation of the particle? For example, could we examine particles before we knew about 'fields' ?

If so... can we examine the fields before we know about particles? Or were the particles necessary for us to even know of the field's existence?

The field... I'm assuming here (and hoping for corrections/validations on these assumptions) there are infinite/MANY MANY different 'fields' in which 'particles' can belong to. But we haven't been able to link all 'fields' together into a single field have we? (Just saying that makes me think of a kind of "Unified field theory" and from that I would have my answer already huh) Hence the labeling of 'particles' elementary...

But are there elementary fields too (that we've identified)? Or perhaps, fields obviously responsible for -other- fields?

17. Feb 12, 2011

### sophiecentaur

Re: What does it mean by a particle is a "wave"

It's interesting that we are seeing a problem with the words "particle" and "wave" but the word "field" is being used as if we knew exactly what it means.

18. Feb 12, 2011

### superpaul3000

Re: What does it mean by a particle is a "wave"

At first, wave-particle duality may seem incomprehensible, but if it is real you can comprehend it. Since many experiments have repeatedly verified quantum mechanics, it is very real. Perhaps weird but definitely real.

To understand the answer you have to understand we are talking about a couple separate things here. First of all, let's begin with some macroscopic object we are used to seeing. Take for instance a light bulb emitting light in the form of oscillations of an electromagnetic field. If you zoom in close enough you realize that that light you were seeing was just the addition of several small packets of light called photons. So here we get our particle part of the duality. The best way to picture this is looking at an LCD screen. Imagine watching a video of waves rippling across a pond. The waves look continuous from far away but when you zoom in you see the quantized version of the LCD field known as the pixel. Keep in mind that we still have not gotten to the wave part. The macroscopic waves mentioned so far are just the addition of all the pixels/particles.

Now the wave part is where it gets interesting. Usually when we think of a wave we imagine some sort of medium like water or even the vacuum of space for gravitational waves. Then a wave is simply the oscillation of that medium propagating out across some distance. Particles traverse the vacuum of space as if it were a medium like a Dirac sea. Waves in this medium are like existence waves. The height of the wave corresponds to the likelihood of the particle existing there. So these existence waves can propagate through a double slit and interfere just like any other wave. When the wave interacts with the measuring screen in goes through a process called decoherence. The particle must have a 100% chance of existing somewhere so all the wave heights must add up to one (for those who know the math I'm talking about <psi|psi>=1). Before the existence wave hits the screen it is very well spread out but as it begins to interact with the screen and decohere, one particular place will begin getting a very large existance wave height until the height grows to one. Then we can say the particle was recorded as existing there.

So what's the problem with all this? The problem is why that particular spot over any other. It seems to have collapsed to a random spot. That's where you get into all the various interpretations of quantum mechanics. Don't let anyone get you hooked on one interpretation or another. The truth of the matter is we don't know why it appears random. So for now just sit back and enjoy the show as we physicists pull our hair out over this problem until it is definitively solved.

19. Feb 14, 2011

### Openeye

Re: What does it mean by a particle is a "wave"

Well what happens when we pick apart the language/ways of understanding things too much too quickly is the thread gets closed. I learned that with my first thread here. Thanks for any clarity you can provide on these 'matters'. :)

20. Feb 14, 2011

### sophiecentaur

Re: What does it mean by a particle is a "wave"

With all these type of discussions it seems to be a matter of relating an acceptable number of 'familiar' concepts to a new and less familiar concept. The problem with QM is that there are a lot of paradoxes if one insists on squaring everything with classical concepts.
If you think you've "got it" then you probably haven't. "Getting it" has to be a very slow and incremental business and, in the end, you find you have accepted the new ideas and cast off from the old familiar stuff, when necessary, without any serious trauma.

You have to don a sort of mental saffron robe, sit cross legged and be 'grasshopper' for a while.