[General] On photon momentum

[ANDREW WORSLEY]

Thanks John,

Thats a good answer waves generally travel through something aka sound waves through air, motion waves through water and seismic waves throught the Earth 
etc. etc. etc.

But consider this a single gamma ray photon would need more energy to create it than all the "space energy" contained withhin the galaxy, which is why the 
scholars at the time had difficulty with it.

So actually and ironically E-M phtons are the exception when it comes to waves they are actually discrete packets of energy with a momentum p= hf/c. and a 
wavelenght, lamda = h/p

See my previous entries.

Andrew


Hi Grahame/All


Heres the answer to the momentum of a photon.

Lets start with the conventional eaquation for the photon

E = hf.

What does that actually mean?

Lets break this down, h is the fundamental quantum of energy.

Actually dimensionally energy multiplied by time, but every thing at the quantum level has a frequency so that's fine. so we have [E].[T]. [T^-1] = E.

But remeber we are talking quantum physics here, so the minimum quantum frequency =1

Or if we are using integers of the value n, then E=hn.

We can liken this to currency, the total amount of money you have is eqaul to the minimum currency (lets say the cent) multiplied by the number of cents.

Equally the total amount of energy you have is equal to the minumum energy currency (h) multiplied by the number of quanta (n) So E =hn.


But waht does that really mean? On a quantum scale lets take a single photon lets say a gamma ray photon with a frequency of 10 ^28. That means it is 
composed of 10^28 fundamental quanta each with the energy h.

So on a comparative level the single quanta would be like the volume of a tiny droplet of water and the single gamma ray photon equivalent to the volume of all 
the water on the planet Earth - so now we are talking quntum physics small small small.


Now if we assume for, now that E= mc^2 is correct, then if our minimum quantum of energy is h then the minumum energy h = mc^2, and by definition the 
minimum mass quantum(mq) is mq=h/c^2.

So waht is the mminumum momentum p of the minimum photon with a single quantum with a velocity c.

Well p = mv = h/c^2 x c = h/c


So the momentum of your photon is p = hn/c or if you prefer to stick with convention hf/c.


Al of this and the rest of quantum physics is readily understandable


See

https://www.researchgate.net/publication/271959433_Everything_is_Physics_Book_1_Understanding_physics_at_the_fundamental_level


Hope this helps 


Andrew















========================================
Message Received: Jan 29 2017, 10:27 AM
From: "John Duffield" 
To: "'Nature of Light and Particles - General Discussion'" 
Cc: 
Subject: Re: [General] On photon momentum

Grahame:



I think of photon momentum as something like the momentum of an ocean wave. See  wind waves 
on Wikipedia and look at the gif:







The wave is motion. Take away the motion and you take away the wave. Note that energy and momentum aren’t two totally different things. One is a distance 
measure of energy-momentum, the other is a time measure. You can’t take the momentum away from a cannonball without taking away the kinetic energy too. 
The same applies to a wave. Also note that when an ocean wave moves through the sea, the sea waves. And that when a seismic wave runs through the ground, 
the ground waves. So when an electromagnetic wave moves through space… space waves. That’s what Maxwell said. See Einstein’s Leyden Address 
. He didn’t think of space as nothing. Also see the stress-energy-momentum tensor 
which “describes the  density and 
flux of  energy and  momentum in 
spacetime”. It’s got a shear stress term:







I think it’s because space is like a ghostly gin-clear elastic. Waves run through it, and matter is made of them. 



Regards

JohnD



From: General [mailto:general-bounces+johnduffield=btconnect.com at lists.natureoflightandparticles.org] On Behalf Of Dr Grahame Blackwell
Sent: 29 January 2017 00:12
To: Nature of Light and Particles - General Discussion 
Subject: [General] On photon momentum



Dear All,

[Notably Chandra & Chip],



I'm having a bit of a problem over this question of: 'How does a photon carry momentum'? (or similar words.)

It seems to me that in order to even beginning to address this question, one needs a clear definition of 'momentum' that's applicable to the momentum carried by 
a photon.

I may be looking in the wrong places (if so please advise), but the only definitions of momentum that I can find either refer to 'mass' or refer to some other 
phenomenon which in turn refers to momentum - i.e. circular references.

If I'm going to figure, or be persuaded, how a photon carries momentum I first need to know what momentum IS in respect of a photon (yes, I know it's E/c, that's 
a measure it's not a definition).

Of course I'm aware of the paper "Light is heavy", but I don't feel it's appropriate just to extract from that some sort of mass-equivalence of a photon. If we do, 
we get the result that 'm'=E/c^2, so 'm'c = E/c - gives the right result, but appears to be some sort of convoluted self-confirmation (i.e. a circular argument 
dressed up in fancy clothes). It certainly doesn't DEFINE a photon's momentum, just evaluates it.



Does anyone have a convincing definition of momentum that's applicable to a photon? One that can be used as a firm basis for theorising?

(I'd be glad if colleagues didn't use this as an excuse to yet again present their own personal theory/model - I'm looking for a definition that would be agreed by 
all, or at least most, physicists.)



Thanks in anticipation,

Grahame