1. Jun 20, 2010

kntsy

I always feel confused about the concept of wave. I don't know why we have to develop a term called "wave"? To me, wave made of particles oscillating up and down periodically.
Is wave just a collection of particles or is wave an identity independent of particles?

For example:
Light a collection of photons
Sea waves a collection moving water molecules
Seismic wave a collection of soil particles
Wave on a string is a collection of string particles

But why do we say that electromagnetic wave is a collection of oscillating electric and magnetic field? Why not say that it is a collection of some particles? To me, field is an abstract idea(cannot be seen/touched) whereas particles exist in nature.

2. Jun 20, 2010

Pythagorean

I've always considered the wave to be a description of the physical dynamics. The particles are just the medium through which the wave is traveling. Also, not all waves (electromagnetic, for instance) require a medium of particles.

3. Jun 21, 2010

americanforest

I'm not sure what is more abstract an idea: fields or point particles which exist in 3 dimensional space and have no mass. I am more comfortable with the former. In the words of Feynman,
. This kind of reasoning points to the field concepts as being the more fundamental.

4. Jun 21, 2010

Staff Emeritus
That may be what it is "to you", but that's not what it is.

Light, for example, is not a bunch of photons "oscillating up and down periodically" - if it were, it wouldn't travel in a straight line. It would travel in a wavy line.

5. Jun 21, 2010

Dav333

But each photon has a wavelength & move up & down don't they? And overall it still travels in a straight line?

6. Jun 21, 2010

K^2

You can always second-quantize a wave, and end up with particles. Particles for sea-waves aren't going to be molecules of water, though. They'll be phonons of some sort.

7. Jun 21, 2010

Staff Emeritus
No. A photon's wavelength is a statement about how the electric field changes over a distance, not a statement that it is bouncing up and down.

8. Jun 21, 2010

sophiecentaur

This subject comes up so frequently and I blame the first person to use the word 'particle' for the Quantum after we moved from the 'corpuscular theory' (which really did treat light as consisting of little bullets) to waves. The wave description makes extremely good sense as it can explain all classical light phenomena.
Quantum theory says absolutely nothing about particles, as such. It merely stipulates that em energy exists in quanta. Using the idea of particles just creates the sorts of misconception that this thread contains. Just how big are they supposed to be and where? The 'two slits' problem gives so many people a hard time simply because they feel they have to visualise little bullets going (or not going) along certain paths. Is the concept of a wave so very hard in itself? QM really just says that the em wave can only carry or interact with integral numbers of characteristic quanta of energy or momentum; no bullets.

The question / statement that should be banned from all serious Science discussions is one involving the words "what it really is", when describing a phenomenon. All we can say is what best describes something in terms we already know and love.

9. Jun 21, 2010

Dav333

Ok. any links for noobies like me on how to further understand this?

Some sites just show you that its a particle & travels up/down.

thanks.

10. Jun 21, 2010

Sarpedon

The word 'wave' comes from waves you have on the ocean or a pool of water. Later it was adapted to other things like sound waves.

No concepts we have every day words for can be used to describe anything related to quantum mechanics or particles. Those obviously aren't things you can experience.

There's only math. Any word you use is merely an analogy.

11. Jun 22, 2010

sophiecentaur

"Some sites" need to be treated with suspicion!
It is very true to say that (transverse) waves travelling through a medium (seismic waves, for example) will involve lateral oscillations of particles and that the oscillations are longitudinal for longitudinal waves. For surface waves (e.g. sea waves and the seismic waves that radiate outwards for a short distance from an earthquake) the motion of individual particles is in a circle - which is not what the majority of School books say. You can verify this by watching (from the side) a can floating on the sea or even by getting in there, near a jetty and watching the way the world moves in a circle when you are floating on a large swell (not necessarily at Monte Carlo LOL).
BUT, the wave is merely 'carried' by the interactions between the particles; it is not the particles themselves. No particles at all are involved when em waves travel through space. However, when radio waves travel through the ionosphere, individual electrons do actually move from side to side as the fields around them vary. That, of course, is NOT photons moving from side to side.

12. Mar 9, 2011

yrreg

Re: Is wave made of particles? Time to be philosophers.

At least any thinking person of some realistic profundity can say that a particle is something as also a wave is something, as opposed to 'a nothing'.

Then describe what that something does in the way of contributing to the operation of the observable and known to man universe (oaktmu) which includes the nose in the face of man.

Always go to the determination is it something or it is nothing absolutely nothing.

If it is something even just a word, then determine what is its contribution to how the oaktmu world works including the nose in the face of man.

Otherwise no one has the business of telling people that:

Above #8:

'The question / statement that should be banned from all serious Science discussions is one involving the words "what it really is", when describing a phenomenon. All we can say is what best describes something in terms we already know and love."

So, scientists here and would-be scientists and also of course science enthusiasts, have a bit of philosophy, here:

1. First determine whether a something really is something as opposed to nothing, even just a phrase like "flying spaghetti monster."

2. Then determine what contribution it makes to the operation of the oaktmu (observable and known to man universe) world of man and his nose.

3. If two things make the same contribution, then look for their what philosophers of old call accidental qualities which can be absent and yet the thing still should continue and does continue to contribute to the operation of the oaktmu world of man and his nose.

There, now you will not anymore abandon a thread when the development is pointing to that direction, owing to your fear of philosophy.

Remember science is a tool for knowledge not a pseudo reason to abandon the quest for knowledge because of your pre-self-dungeoned world whereby you already put yourselves inside a dungeon outside which you dare not go because otherwise you would be a what? heretic!

Yrreg

13. Mar 9, 2011

Drakkith

Staff Emeritus
Yrreg i don't think you understood anything that sophie was saying in that post.

14. Mar 10, 2011