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Deepak K Kapur
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Photon's rest mass is zero.
What's its 'moving' mass?
Thanks.
What's its 'moving' mass?
Thanks.
It does not have mass, it has momentum. I'll have to leave it to others to explain that in more detail, or you can try this site:Deepak K Kapur said:Photon's rest mass is zero.
What's its 'moving' mass?
Thanks.
It has energy, so you can calculate a "moving mass" for it from ##E=mc^2##.Deepak K Kapur said:P
What's its 'moving' mass?
As I was replying mass is energy so you can get rid of the concept of mass and think just Chuck of energy "flying off".Deepak K Kapur said:I have understood something from the link..
But, here are a few questions.
1. Photon's rest mass is zero. It's energy is also zero.
It means it is non existent. So, why to define such a term in science " rest mass of a photon "?
2. When photon is emitted by an electron in an atom, does it mean that the photon did not exist prior to its emission in any possible way? It seems to be creating something out of nothing (in a way).
Or, was the photon present in the electron in some rudimentary form?
Deepak K Kapur said:1. Photon's rest mass is zero. It's energy is also zero.
Deepak K Kapur said:2. When photon is emitted by an electron in an atom, does it mean that the photon did not exist prior to its emission in any possible way? It seems to be creating something out of nothing (in a way).
Frost_Xue said:As I was replying mass is energy so you can get rid of the concept of mass and think just Chuck of energy "flying off".
No, it's energy is not zero. I am not sure what would lead you to believe that, but it is incorrect.Deepak K Kapur said:It's energy is also zero.
Yes, that is correct. The photon is created by the atom relaxing.Deepak K Kapur said:does it mean that the photon did not exist prior to its emission
Dale said:No, it's energy is not zero. I am not sure what would lead you to believe that, but it is incorrect.
ZapperZ said:
Deepak K Kapur said:I do.
BTW, what are you for, writing FAQs??
Drakkith said:It did indeed not exist prior to emission. It was created from the interaction between the atom and the EM field, and its energy comes from the atom. The atom loses energy equal to the amount gained by the photon.
Deepak K Kapur said:I can understand when hydrogen and oxygen atoms combine to form water (electron transfer etc.)
What is the mechanism of interaction of the atom and the EM field that leads to the release of this photon.
(other than the mathematical mechanism)Something like...
The electrical and the magnetic elements of the incoming photon separate inside the electron and then combine again depending upon the energy of the level that the electron returns to...
Deepak K Kapur said:How can something that has no mass at all, have energy!
Deepak K Kapur said:Aren't mass and energy interchangeable.
Deepak K Kapur said:So, if photon at rest has energy
There is no such thing as a photon at rest (because they always move at the speed of light) and therefore it is meaningless to speak of the energy of a photon at rest.Deepak K Kapur said:So, if photon at rest has energy, can't it be said to have mass also?
What is the good reason then?Drakkith said:Photons have non-zero energy.
It did indeed not exist prior to emission. It was created from the interaction between the atom and the EM field, and its energy comes from the atom. The atom loses energy equal to the amount gained by the photon.
Not quite. There's a good reason the term mass is still around. Mass and energy are related, but they are not the same thing.
As I said above. The relationship between energy, momentum, and mass is: ##m^2 c^2=E^2/c^2-p^2##Deepak K Kapur said:How can something that has no mass at all, have energy
IF a photon could be at rest and have energy then it would have mass, BUT in reality a photon is never at rest and does not have mass.Deepak K Kapur said:So, if photon at rest has energy, can't it be said to have mass also?
Frost_Xue said:What is the good reason then?
Yea, please let me know that would be very helpful thanks a lot!Drakkith said:Hmm... I thought I had a link that explained it, but I can't seem to find it. I'll keep looking.
Deepak K Kapur said:What is the mechanism of interaction of the atom and the EM field that leads to the release of this photon.
(other than the mathematical mechanism)
Nothing whatsoever, not in the slightest.Ethan Santillan said:Is this has something to do with Higgs-Boson Field?
Dale said:PLEASE, examine carefully the equation that I have posted twice now before you respond again.
I think you are wrong on this. The math IS the concept, in the best language that we have developed for understanding and communicating such concepts. Any natural language description is merely a rough translation.Deepak K Kapur said:I think (may be wrongly) that math comes later than concepts. I am after the concept here...
A force is a change in momentum. What does the equation tell you about momentum and mass? Are they the same thing?Deepak K Kapur said:I think I surely would have to apply force just as now I apply force to stop a ball.
1. Isn't this mass?
It can't be brought to rest, as has been explained multiple times already.Deepak K Kapur said:2. When I stop a ball it doesn't stop existing ( i.e. lose its mass). Why would a photon become massless if I bring it to rest?
Yes photons are already moving at c when they are produced. This is not magic, it is conservation of momentum and energy. The same considerations determine the initial speed of any newly created particle.Deepak K Kapur said:From the replies it seems that photons are already moving at the speed of light when they are produced...
Why? What is this going on... a magic show!
Deepak K Kapur said:From the replies it seems that photons are already moving at the speed of light when they are produced...
Why? What is this going on... a magic show!
Not a magic show, because it's real... And that makes it incomparably more exciting and interesting than any sleight-of-hand magic show.Deepak K Kapur said:From the replies it seems that photons are already moving at the speed of light when they are produced...
Why? What is this going on... a magic show!
The concepts come from the math and not the other way around. Math is the language of physics, so trying to understand the physics before you do the math is like trying to understand a book written in a language you don't know by looking at the pictures.I think (maybe wrongly) that math comes later than concepts. I am after the concept here.
Deepak K Kapur said:I will continue to post in this thread under this assumption only...
To expand slightly on Drakkith's question:Deepak K Kapur said:Thanks everyone for their intelligent answers.
I hope nobody gets irritated by my questions. I will continue to post in this thread under this assumption only...
.
Drakkith said:What assumption?
ZapperZ said:Drop a stone into a pool of water and look at the ripples produced. Do you see it "accelerating" from zero velocity, or does the wave already move at a certain speed when it is produced?
This "magic" is already all around you, even in such ordinary observation as water waves. It is so familiar even if you are not aware of it.
Your question on how something can exert a force, or needs to have a force exerted on them, and yet not have mass, is why I often tell people that you can't learn physics in bits and pieces. You see, way back in the 1800's, before the concept of photons even came into existence, light was known to be a classical wave, described via Maxwell Equations. There was no concept of particles here.
Yet, even back then, they already have a knowledge of "radiation pressure", meaning they already have a description of light pushing against something, i.e. imparting a force. Yet, nowhere in the formulation of light at that time was there ANY involvement of "mass" for this entity.
Texts on classical E&M still have this concept. So already, the insistence that having a force must equate to having a mass is faulty.
Zz.