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Author Topic: does photon has mass?  (Read 1601 times)

Offline rocking_1987

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does photon has mass?
« on: 01/08/2012 20:52:58 »

If electron gets the energy and release the energy in the form of the light, how could electron make a photon from its mass? Can we produce unlimited light by giving the unlimited controlled energy to the electron?
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I have come to know that it is still not clear that if photons has mass or not?

So I have questions in the both situations:

1) if it has a mass: If photons has mass than does it mean that every time electron produces the light it is loosing it mass also? Does it mean electron may lost its negative charge as well? How long electron can produce the photon?

2) if it does not has a mass: If photons does not has the mass than why gravity affects it? Why black hole's gravity does not allow light to escape it? How come it can trap the energy, if photons do not have the mass? Is it mean that energy can be stored if you have enough gravity?



 

Offline Pmb

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Re: does photon has mass?
« Reply #1 on: 01/08/2012 22:30:05 »
If electron gets the energy and release the energy in the form of the light, how could electron make a photon from its mass?
A real electron can never absorb a real photon nor emit a real photon. Therefore an electron can never produce a photon from.

Can we produce unlimited light by giving the unlimited controlled energy to the electron?
This doesn't make sense to me. Perhaps you can explain it to me?

In the first case its not possible to produce an unlimited light. But let's say that for all practical purposes we can do it in reasonable amounts at a continuous rate, such as a HeNe laser with a source that won't run dry for few thousand years. We cannot give this to an electron because they can't store energy.

I have come to know that it is still not clear that if photons has mass or not?
It is very clear in the physics community whether light has mass or not. The only problem being that some people quibble about what the term mass means when it is unqualified. That's why I always try to refer to it as inertial mass when I remember to. That way nobody is confused. But there are still people out there who complain when people use the term inertial mass different then they do. It's really irritating.

That said, the proper mass of a single photon is zero while the inertial mass of a single photon is not zero.

For us to help, you we need to clarify what you mean when you use the term mass unqualified. Do you mean inertial mass or proper mass? Are you familiar with these terms?  Inertia mass is the m in

p = mv = m(v)v = m0v/sqrt(1 -v/2c2)

Proper mass is the m0 in that equation. It has the property that

m0 = limit (v->0) m(v) = m(0)

They're related by the expression

m = m0/sqrt(1 - v2/c2)

Until I know what you mean I'll assume you mean inertial mass until you state otherwise.
So I have questions in the both situations:

1) if it has a mass: If photons has mass than does it mean that every time electron produces the light it is loosing it mass also? Does it mean electron may lost its negative charge as well? How long electron can produce the photon?
Since you're assuming that electrons are producing light when it really can't then I can't answer it.

2) if it does not has a mass: If photons does not has the mass than why gravity affects it? Why black hole's gravity does not allow light to escape it? How come it can trap the energy, if photons do not have the mass? Is it mean that energy can be stored if you have enough gravity?
Since photons have energy they also have gravitational mass. This means that it can be acted on my a gravitational field and it can generate a gravitational field.
 

Offline Soul Surfer

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Re: does photon has mass?
« Reply #2 on: 02/08/2012 00:03:28 »
While Pmb is right with what he is saying there is one important fact that needs to be remembered. While an electron travelling on its way with any sort of energy undisturbed cannot produce photons.  If the motion of the electron is disturbed by an electromagnetic field it does produce photons so if you have electrons or any other charged particles forced to go into an orbit by feeding energy into them they generate what is known a synchrotron radiation.

Particle accelerators are often used to produce high intensity very energetic radiation not just energetic particles.

In this way although the electron loses energy every time it generates some photons as you are continually feeding energy into the electron a given electron in an orbit can produce photons without limit.
 

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Re: does photon has mass?
« Reply #2 on: 02/08/2012 00:03:28 »

 

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