Ask any question you want about Physics

originally posted by: BASSPLYR
a reply to: Bedlam

Took me a second but makes sense now.

It gets down to a sheaf of probabilities...any one photon can be anywhere but is more likely to exist in a radius along the path it's taking, that radius is smaller the higher the frequency.

Think of it as (this is awful) tinkerbell flying a straight path in a fog bank. YOU see a ball of light that initially seems tightly bounded but as you look at it, it is obviously lighting up the fog around it to a much lesser extent past the radius, but it does light it up.

As tinkerbell is more red, the radius of that ball is larger, bluer, smaller.

The ball is the volume of non-negligable wave energy. The ball AND the backlighting are the locus of probabilities of the photon's location.

eta: from an engineering pov, the photon is the ball. From a physicist's pov, it's the dead center of tinkerbell's .... hind end. She could be anywhere, but more likely at any moment to be in the ball somewhere.

originally posted by: BASSPLYR
a reply to: BASSPLYR

So a photons intrinsic energy is always the same? A photon is a photon is a photon, but the space it takes up makes the frequency. The more energized the more condensed? The number of photons in a stream of photons (not sure stream is the right word) is the amplitude?

Photons can have various amounts of energy. What varies with that energy is the frequency, which goes up, and the wavelength, which goes down. The radius of non-negligable wave energy shrinks with the wavelength, and the energy density in the volume increases. The speed stays the same. There is no amplitude. From a physics pov, the photon's particle size doesn't change. From an engineer's, the wave tightens up and 'gets smaller'. Eros and mbkennel will hiss and hold out slide rules to repel me for that statement. But that's how we're taught to 'see it', although it's less a visualization than an understanding.

Yes, the number of photons in a stream is the amplitude.

a reply to: Bedlam

this is actually very helpful. when you mean non negligible what exactly do you nnean. I take non negligible in general to mean not worth measuring or impact of as too trivial.

I'm beginning to understand this visually with your help so don't stop now n give me blue photons before I can reach a climax and resolution in my understanding here.

I'm a visual person, when I play music I visualize geometrically the relationships between the harmonic series with the tonic or key, i also get synthesthesia and see tones as colors, but that's a different story, the point is I'm visual. so when i think of frequency in photons I'm thinking here's a photon it has a Set amount of energy which will take up this much volume if set in the middle of the dial say a midrange frequency. turn the dial up the energy amount stays the same but the volume it inhabits shrinks so the photon is smaller but denser energy wise. more photons can be potentially packed in the same space as the previous midrange photon thus increasing the frequency they can appear and net potential energy in that wave packet can go up granted there are the actual numbers of photons to facilitate said amplitude? color changes to blue. turn the dial down the same amount if energy that was in the midrange frequency gets diluted or stretched out over a larger volume increasing the radius and decreasing the uperlimit if potential amplitud possible since the photon is physically larger (sort of) color changes to red.


that's how I'm visualizing amplitude and frequency in the photon........so as you can see me need help getting my smarts good. will you help bassplyr caveman brain to understand better. also know good tailor who can make suit with cuff length longer than inseam?

a reply to: BASSPLYR

As long as you're using the engineering 'wave energy' shorthand of photon size, it's pretty close.

The physics version will tell you the actual particle has no extent at all. Which is true. You have to collapse the wave function (that's the ball around Tinkerbelle) to find where the physics particle photon was. But the engineering wave view, it's about the radius of a half wavelength. Inside that volume, you'll find the majority of the wave energy. The rest of it trails off forever. But the bulk of it's in there.

Photons rarely interact and can easily have overlapping wave functions. So it's not like you can get more or less of them in a beam depending on frequency. They can collide but it's rare.

Actually, it's not a set thing on the energy, either. The more you pump in, the smaller it gets. So it's denser and more energetic in the smaller volume. Both.

a reply to: Bedlam

very cool bedlam. I think I understand better now.

so why is there no charge to the photon?
also if you can get the occasional photon to collide with enough regularity could you in effect produce matter?

originally posted by: BASSPLYR
also if you can get the occasional photon to collide with enough regularity could you in effect produce matter?

Dashen said this on p231 and it's right, but I don't know if this has actually been observed from 2 photons colliding, though it's statistically predicted to occur rarely. You didn't say what you wanted the photon to collide with.

originally posted by: dashen
In a high-energy photon collision a positron electron pair is formed.

so why is there no charge to the photon?

If it does have a charge, it must be really, really, really small.

Bound on the Photon Charge

If the photon possessed a nonzero charge, then electromagnetic waves traveling along different paths would acquire Aharonov-Bohm phase differences. The fact that such an effect has not hindered interferometric astronomy places a bound on the photon charge estimated to be at the 10^(-32) e level if all photons have the same charge and 10^(-46) e if different photons can carry different charges.

I haven't seen a non-circular explanation for why the photon has no charge. I've seen explanations for why it can't have a charge and still behave like a photon, but again that doesn't really answer the question. Why should it have a charge? If you don't know of any reason why it should, isn't that sufficient reason for it not to?

It has to have rest mass. At least enough to have an electron or positron on its back. So no rest mass = no charge. Teensy rest mass (neutrino) not big enough to carry any.

You see, particles are little balls of painted wood. If it's smaller than a black ball, it can't have an electron or positron inside.

eta: I still haven't figured out a non-totally-deceitful/confusing way to tell you how a photon doesn't have anything 'waving up and down' like the bad explanatory drawings I see and which has confused more than one person on the thread.

a reply to: Arbitrageurm.phys.org...

Maybe he means this.

a reply to: dragonridr
Yes, that's why I said I don't know if it's actually been observed, and I still don't. The way that article is written it sounds like the experiment can be quickly performed with off-the-shelf technology and that was back in 2014 and it's 2016 now so I wouldn't be too surprised if it's already been observed and maybe just not published yet.

First, the scientists would use an extremely powerful high-intensity laser to speed up electrons to just below the speed of light. They would then fire these electrons into a slab of gold to create a beam of photons a billion times more energetic than visible light.

dashen called them "high-energy photons", and the pair production won't happen at less than a million times the energy of visible light but a billion times the energy of visible light sounds like it's enough.

Is there an upper limit to a photon's wavelength? Theoretically could a photon have a wavelength greater in size than the universe?

a reply to: Poon
I am sure there are several good arguments from uncertainty principle, as well as others, but to me the energy consideration is a practical argument against a photon with a wavelength a significant fraction of the diameter of the universe. The energy carried by a photon E=(hc)/(lambda) approaches zero as the wavelength increases. At some point much before the wavelength becoming universe-sized, the energy of the putative photon is so low that it will not cause interactions with anything. Thus, to an engineer it might as well not exist even philosophically.

a reply to: Arbitrageur

What is the difference between a single high energy photon and a single low energy photon?

originally posted by: ImaFungi
a reply to: Arbitrageur

What is the difference between a single high energy photon and a single low energy photon?

Wavelength. That is all.

a reply to: Bedlam

And the cross section

originally posted by: Bedlam

originally posted by: ImaFungi
a reply to: Arbitrageur

What is the difference between a single high energy photon and a single low energy photon?

Wavelength. That is all.

But you just said in reality, photon has nothing to do with wave.

I just noticed the wiki page for Photon has taken down the image that me and Arb used to discuss, of the electric and magnetic separate fields moving in their ways to create the concept of a true up and down moving wave.

Has science recently grown into the belief that photon has nothing to do with wave?

originally posted by: ImaFungi

originally posted by: Bedlam

originally posted by: ImaFungi
a reply to: Arbitrageur

What is the difference between a single high energy photon and a single low energy photon?

Wavelength. That is all.

But you just said in reality, photon has nothing to do with wave.

I just noticed the wiki page for Photon has taken down the image that me and Arb used to discuss, of the electric and magnetic separate fields moving in their ways to create the concept of a true up and down moving wave.

Has science recently grown into the belief that photon has nothing to do with wave?

Where did I say that? I did say that photons have both wave aspects, which as an EM engineer I am most likely to use, and particle aspects, more useful (at times) for physics. Both are real.

However, the wave doesn't "move up and down". You're one of the people on the thread that seems to bother. But it's a common misconception, caused by visualizing things.

originally posted by: Bedlam


eta: I still haven't figured out a non-totally-deceitful/confusing way to tell you how a photon doesn't have anything 'waving up and down' like the bad explanatory drawings I see and which has confused more than one person on the thread.

Ok so. It doesnt have anything waving up and down, because that would imply some kind of possession, as a ship has a flag waving up and down, the photon doesnt have anything waving up and down;

But, is the photon itself, waving up and down?



O

Imagine that is a perfect particle.

That can be called a particle.

That particle can move

O ---------------> O
a ---------------> b


That particle could be considered 'wave like' if while it moved from a to b

It did so, relatively up and downward.

The concept of a photon being a wave, and only being a wave

is the concept of a snake being able to wiggle, or imagining if a snake could do nothing but continuously wiggle.

Either a photon is more like a marble (A) or a snake (B).

A)Either a photon, being more like a marble, tends to travel in a relatively direct straight line; or the photon being more like a marble tends to travel due to its internal nature and/or continuous interaction with surrounding, travels in an up and down or side to side or spiral pattern;

B)Or a photon is more like a snake. and it itself, does not travel up and down momentously, but its body is the continual traveling of up and down while remaining traveling straight.

Do you know which it is more like? Do you know. Do you know. do you have a clue?


Stop making it so complicated, the truth is very simple, the only reason it is complicated is because you do not know the truth.


When you do not have any idea of the truth, you tend to try to be funny and patronize me, lets objectively observe how you respond to my very clear and concise points.

originally posted by: ImaFungi

Ok so. It doesnt have anything waving up and down, because that would imply some kind of possession, as a ship has a flag waving up and down, the photon doesnt have anything waving up and down;

But, is the photon itself, waving up and down?

No.

a reply to: Bedlam

So having tinsy rest mass thats not really worth accounting for. Photons, Neutrinos etc. I'd love to talk about those.

What do scientists think the neutrino is made of? Same question for quarks.

Like a proton has a. A down quark and two up quarks, And associated Neutrinos. Some Glueons etc. Whats causing the positive charge inside the proton that keeps the electron attracted to the proton and orbiting? A hidden positron floating below the zero point or something? Why do Protons have a negative charge at all?

Whats the neutrino and quarks made up of?

Could there be like a fundamental building block that these leptons (electrons, positrons, tau, omega-, associated neutrinos) are made of? Same question for the Quark. Are they all just manifestations of multidimensional vibrations like speculated in string theory? Something more going on there?

a reply to: Pirvonen
That's a good answer, thanks.

So, could a photon with such low energy that it can't interact be classified as a type of dark energy?