Does a controversy still exist ?

[alfredblase]

Would it be right to say that a Quantum Mechanical object, be it light or any other, is a point particle, with a time dependent probability distribution for its position, energy, interaction with other objects, and so on and so forth? Yes or no would do please although more would be nicer. Thanks.

 

[McQueen]

you have metallic plants??!

Come on now ! With metals everything is reflected ( absorbed and re-emitted ,with other objects there is selective absorption and emission.

 

[ZapperZ]

Come on now ! With metals everything is reflected ( absorbed and re-emitted ,with other objects there is selective absorption and emission.

Yeah, but you were using my explanation of the mechanism in METALS, and using that inappropriately to describe the reason why we see colors in objects that aren't metals! Do you think this is kosher?

Again, as I've stated way earlier in this thread, it appears as if your primary source of info on physics is based on what you read on the web, and not anymore more formal than that. I would be very weary of such sources if I were you. Things like what you're doing here will occur often.

Zz.

 

[McQueen]

Again, as I've stated way earlier in this thread, it appears as if your primary source of info on physics is based on what you read on the web, and not anymore more formal than that. I would be very weary of such sources if I were you. Things like what you're doing here will occur often.

Can you make some time. If you leave me in the air it means , we wouldn't see colours or anything else. AND what's wrong with things on the web? Also I have some great Russian books , so don't dis me on that account. (P.S., not weary BUT wary)

 

[ZapperZ]

Can you make such time. If you leave me in the air it means , we wouldn't see coulours or anything else.

Say what? Are you still claiming that your hijack of my explanation for optical process in metals is valid when applied to insulators?

AND what's wrong with things on the web?

1. How would you know the stuff you read off the web is valid, or even correct? As much as I like and refer to Hyperphysics, I can STILL find things that I find misleading or incorrect.

2. They lack RIGOR and details

3. Physics isn't just "reading" off anything. You miss a lot simply by reading only. This is not a literature class. You could read till you're blind how to ride a bicycle, but unless you actually get on one, do it a few times, fall off it a few times, you will never be able to ride a bicycle. Physics is as much knowledge as it is a SKILL. Skills cannot be taught - it can only be ACQUIRED.

Zz.

 

[McQueen]

2. They lack RIGOR and details

I could give you a higly detailed summary of your spectroscopy experiments with multi- photon photoemission , unfortunately it didn't download properly , so I saved it as a word document. So I don't have the URL , still you see what I mean.

3. Physics isn't just "reading" off anything. You miss a lot simply by reading only. This is not a literature class. You could read till you're blind how to ride a bicycle, but unless you actually get on one, do it a few times, fall off it a few times, you will never be able to ride a bicycle. Physics is as much knowledge as it is a SKILL. Skills cannot be taught - it can only be ACQUIRED.

That's just it I have been thinking. and you still haven't answered my question , " metals reflect everything , coloured objects use selective absorption and emission. Or is this too big a subject to undertake? P.S. Anyone can ride a bicylcyle , even a chimp.

 

[ZapperZ]

I could give you a higly detailed summary of your spectroscopy experiments with multi- photon photoemission , unfortunately it didn't download properly , so I saved it as a word document. So I don't have the URL , still you see what I mean.

A "DETAILED SUMMARY"? What is THAT?

That's just it I have been thinking. and you still haven't answered my question , " metals reflect everything , coloured objects use selective absorption and emission. Or is this too big a subject to undertake?

What does this have anything to do with your explanation? You were using electron transition to explained everything by hijacking my explanation of optical processes in metals. I asked you to justify such a usage. You never did.

And oh, I would think twice before saying that metals reflect everything. Find out the plasma frequency of the conduction electrons and see what happens if I have light at a frequency GREATER than the plasma frequency. And while you're at it, if metals reflect everything, why does it become hot when left in the sun? Could it mean that, horrors, it actually absorbs the IR part of the spectrum? NO!

P.S. Anyone can ride a bicylcyle , even a chimp.

And even a chimp can spew back everything he was told but without understanding what they all mean.

Zz.

 

[McQueen]

And even a chimp can spew back everything he was told but without understanding what they all mean

I am sorry I apologise for the statement.

And oh, I would think twice before saying that metals reflect everything.

I was referring to visible light.

What does this have anything to do with your explanation? You were using electron transition to explained everything by hijacking my explanation of optical processes in metals. I asked you to justify such a usage. You never did.

What do you say about this then ?

etc.. are all techniques that were built using the photon picture, NEVER using "wave" picture of light.

 

[ZapperZ]

I was referring to visible light.

No, you were not. Besides, what is so special about visible light? It is, in fact, a VERY limited range of the EM spectrum. Our physics should NOT work only for that small range. If you are limiting your explanation to only this, then your explanation has serious fault, not that it hasn't already.

Please go back and read my objection here. You were using my explanation using conduction electrons in metals to explain the optical properties of NON METALS. I do not know how much more I can emphasize on how WRONG this is. YOu can't simply repeat what I said without understanding it, and then use it in the wrong situation.

What do you say about this then ?

And I'd ask you "What's wrong with that?" Open G.D. Mahan's "Many-Particle Physics" text and see why optical conductivity experiments CAN and DOES use QM's description of light as the foundation for all such experiments.

This has become a convoluted thread. It seems that every explanation I gave, I have to double-back and have to explain the explanation, and then have to explain that too! Whenever things like this happen, it is usually a symptom that some very fundamental understanding is lacking. While I don't mind going one or two layers deep in trying to explain things, you will understand that at some point, this gets very tiring and exasperating. I can no longer assume that you know such-and-such to be able to comprehend my explanation, and certainly not after you misrepresented my explanations. This thread has taken way too much of my time with no apparent benefit or progress.

So stick a fork in me, because I'm done. Someone else who probably have more patience and can explain things a lot better may want to take over.

Zz.

 

[McQueen]

This has become a convoluted thread. It seems that every explanation I gave, I have to double-back and have to explain the explanation, and then have to explain that too! Whenever things like this happen, it is usually a symptom that some very fundamental understanding is lacking. While I don't mind going one or two layers deep in trying to explain things, you will understand that at some point, this gets very tiring and exasperating. I can no longer assume that you know such-and-such to be able to comprehend my explanation, and certainly not after you misrepresented my explanations. This thread has taken way too much of my time with no apparent benefit or progress.

I'm sorry ! You know I expected something like this to happen , because your work is very detailed and requires your total attention.I appreciate both what you are doing and your level of competence. I'm sorry for distracting you. I just wanted to know how ordinary objects reflect light . How we see things. You have been very patient and I appreciate that.

 

[jtbell]

AND what's wrong with things on the web?

In addition to the points that Zz made, I'd like to add:

4. What you find on the Web, even if it's correct, is likely to be in "bits and pieces" scattered on various Web sites, and not organized in a coherent way, such as you find in a good textbook. If you want to really learn a subject, you need to do it systematically, and do exercises along the way to test your knowledge. Textbooks are (at least ideally) orgainzed to make this possible.

Many professors put lecture notes on the web, and some of them are very good. But these are also "bits and pieces", they may have mistakes because they haven't been reviewed and proofread the way a textbook would have been, and they are usually meant as a supplement to a textbook, not as a replacement for one.

While I'm at it, I have a completely off-topic question for you. :) Why do you put spaces both before and after punctuation marks such as periods, commas and question marks? It sometimes causes a punctuation mark to appear by itself at the beginning of a line in my browser, which looks strange. Remember that everyone's browser will re-wrap your text according to the width of the window that they are using.

 

[alfredblase]

I reaaallly don't want to be a pain or anything but my question is in danger of being relegated to a previous page so I have to restate it. If I am being irritating, foolish or ignorant in making it three times please tell me and I will cease, no hard feelings. It just seems people are very touchy in this thread so I'm not sure what posting guidelines apply...

Anyway the question is:

Would it be right to say that a Quantum Mechanical object, be it light or any other, is a point particle, with a time dependent probability distribution for its position, energy, interaction with other objects, and so on and so forth? Yes or no would do please although more would be nicer. Thanks.

One thing I would say though ZapperZ is that I have done three or more modules on QM. Ok so I didn't get the basics down too good (as I demonstrated in one of my posts), but nevertheless if after a good MPhys degree I am still not sure abouthow to concieve a QM object then there are some serious conceptual shortcomings, perhaps not with the theory itself, but atleast with those who undertake to be our mentors in the subject. And no I don't think its my fault because so many people ask the same question, how do we concieve a QM object and no-one as far as I know has ever given a clear answer, even to people who know a lot of QM maths! (though perhaps still very little relatively, but FGS hwo much maths do you need to forcefeed yourself before a bit of enlightenment comes your way? And no being able to solve/rearrange lots of equations does not necesarily mean you understand physics, it means you understand maths, an important though not stand alone part of physics)

Oh and its all very well saying look in a textbook jtbell but some of us don't have convinient access to a decent library nor have the money to buy the textbooks we need. The internet therefore becomes our only source of information other than the few textbooks and notes that we already have. One of the reasons I love PF, if you can't find it on the net you can ask here hopefully, and perhaps even contribute a little.

Anyway the real point of my post is that someone should kindly answer my question: Would it be right to say that a Quantum Mechanical object, be it light or any other, is a point particle, with a time dependent probability distribution for its position, energy, interaction with other objects, and so on and so forth?

 

[jtbell]

Would it be right to say that a Quantum Mechanical object, be it light or any other, is a point particle, with a time dependent probability distribution for its position, energy, interaction with other objects, and so on and so forth?

Yes, with the addition that the probability distribution is not the fundamental "thing" that QM deals with in its equations. Instead, the fundamental "thing" is the complex probability amplitude \psi(x,y,z,t). This is what the Schrödinger equation actually determines. The position probability distribution is P(x,y,z,t) = \psi^\star \psi. We can also calculate probability distributions for other physical quantities, from \psi, but it's more complicated.

 

[alfredblase]

Thank you very kindly indeed, everyone I have read a post by here seems really nice btw =) Ok so everyone trained in the subject sufficiently, (not necessarily a great deal) can concieve what light is. Why is there so much mystery attached to QM still then, why have there been 104 posts in this thread?? I mean if people in the know have the simple enough explanation confirmed by jtbell, why don't they just give it every time they are asked what is light: a wave or a particle? If they get stuck on the probability bit just tell em to play with a coin for a while heh, and interactions... just say what's the chance I'm going to hit you? and position well just say, errm that's another story hehehe :P but check up on a conceptual explation of Heisenbergs uncertainty principle its rather interesting... and if you know it and have the patience, why not give it yourself? The actual mechanics of the thing.. do the maths xDDD

 

[Ro69]

no it would not

 

[alfredblase]

now we have a contradiction, Ro69 says nay, jtbell says yay. I tend to trust jtbell's answer more as he is a science advisor and he agrees with me, and he put some details in too.

 

[McQueen]

now we have a contradiction, Ro69 says nay, jtbell says yay. I tend to trust jtbell's answer more as he is a science advisor and he agrees with me, and he put some details in too.

But then we would have to go into what P(x,y,z,t) = \psi^\star \psi stands for , which leads to the disassociation of light and so on. Even on the question of the transition of light there are many explanations , with the classical wave explanation and the QED explanation.

 

[alfredblase]

Like Hurkyl first said all those posts ago, according to QM, light is neither a classical particle nor a classical wave.

Light (according to QM) is a quantum mechanical dimensionless particle with a probability density function for all its properties.

And QM is the most widely accepted theory and with good reason.

 

[Physics Monkey]

As Julian Schwinger noted in his excellent text on Quantum Mechanics, the classical world can be divided into two camps, the discrete and the continuous. A tension exists between these two extremes within classical physics and this tension led the early founders of quantum theory to talk at great length about the mysterious wave particle duality. As we grew in understanding it became clear that this silly classical duality is simply our attempt to force a classical interpretation on what is really a quantum unity. The photon is a quanta, neither classical wave nor classical particle. This is why practicing physicists don't talk or worry about some sort of silly wave particle duality. In my opinion, people who insist on talking about the wave particle duality are people who refuse to give up their classical notions (and of course those who are honestly learning). For these people, everything must be a classical wave or a classical particle, but nature has said otherwise.