does light or light waves have mass?
回答 (15)
2019-03-05 6:09 pm
light is massless...
2019-03-05 11:13 pm
No.
2019-03-05 9:06 pm
It is all rather confusing because we often hear that there is a mass-energy equivalence and light sure has energy.
But there is also effectively a momentum-energy equivalence based on the frequency alone.
And the mass-energy equivalence is really the rest mass, which is zero for light (it can't rest).
All of light's energy is momentum based, ie due to frequency alone.
So we consider light has no mass.
But there is also effectively a momentum-energy equivalence based on the frequency alone.
And the mass-energy equivalence is really the rest mass, which is zero for light (it can't rest).
All of light's energy is momentum based, ie due to frequency alone.
So we consider light has no mass.
2019-03-05 8:08 pm
The correct relativistic equation for the energy of a particle is
E = sqrt( (mc^2)^2 + (cp)^2 )
where p is the particle’s relativistic momentum.
A massive particle at rest (p=0) has energy E = mc^2.
A massless particle has energy E = c p
Now note that a photon is a massless particle and quantum mechanics tells us (de Broglie’s relation) that momentum and particle wavelength λ are related as
p = h/λ
But as always λ= c/f, so
E = c p = c h/λ = h f
This therefore gives us Planck’s relation E=hf for the energy of a photon. Neat isn’t it?
E = sqrt( (mc^2)^2 + (cp)^2 )
where p is the particle’s relativistic momentum.
A massive particle at rest (p=0) has energy E = mc^2.
A massless particle has energy E = c p
Now note that a photon is a massless particle and quantum mechanics tells us (de Broglie’s relation) that momentum and particle wavelength λ are related as
p = h/λ
But as always λ= c/f, so
E = c p = c h/λ = h f
This therefore gives us Planck’s relation E=hf for the energy of a photon. Neat isn’t it?
2019-03-06 12:54 am
No, massless.
2019-03-05 8:54 pm
well, that is a good question. the common paradigm says that light has no "mass" but has a mass equivalent to its energy via E=mc^2 (or via the momentum equation because light also has momentum). The idea is simply that there is no mass unless you convert the energy into mass, in which case it is no longer light.
2019-03-06 6:28 am
We have been arguing about this for at least 100 years with different answers at different times.
If you want a DEFINITIVE answer you have come to the wrong place.
Today's best guesses and beliefs will be challenged and overturned in the future as we learn more.
They have momentum. If momentum was viewed as mv then they would have mass.
if momentum is NOT viewed as mv then they do not have mass.
The reason for the argument is that we cannot stop a large number of photons, put them in a container and measure the mass.
Once they are stopped or slowed they cease to exist.
Any mass they may, or may not, have only is present while the light continues to move unabated.
So the photon is not like any solid particle that you might imagine
The basic argument is whether mass is CONVERTED to energy when it becomes a photon or whether energy HAS mass.
Both views rely on E= m c^2
If you want a DEFINITIVE answer you have come to the wrong place.
Today's best guesses and beliefs will be challenged and overturned in the future as we learn more.
They have momentum. If momentum was viewed as mv then they would have mass.
if momentum is NOT viewed as mv then they do not have mass.
The reason for the argument is that we cannot stop a large number of photons, put them in a container and measure the mass.
Once they are stopped or slowed they cease to exist.
Any mass they may, or may not, have only is present while the light continues to move unabated.
So the photon is not like any solid particle that you might imagine
The basic argument is whether mass is CONVERTED to energy when it becomes a photon or whether energy HAS mass.
Both views rely on E= m c^2
2019-03-05 2:51 pm
Yes it does. Remember E=mc^2
2019-03-06 10:27 am
Photons transfer light energy and have.no mass ......
2019-03-07 1:11 am
Atomic mass structure are basically formed from the particle of light.Hence it is the mass of light that composes the mass of an atom. And atoms have not been proven mass less.
The sun loses mass in the form of light rays.The more mass the sun loses the more rays are absorbed by the Earth's atomic structures.
Waves are basically disturbance in a medium.Hence light rays disturb the medium of space structure.
Waves are basically moving forces.
So far the standard model of physics does not indicate or prove that light is mass less.
The equation of energy ;E=MC^2 indicates that only the particles of light can move at the speed of light.
Hence M in the Einstein equation is the summation of light massiveness
The sun loses mass in the form of light rays.The more mass the sun loses the more rays are absorbed by the Earth's atomic structures.
Waves are basically disturbance in a medium.Hence light rays disturb the medium of space structure.
Waves are basically moving forces.
So far the standard model of physics does not indicate or prove that light is mass less.
The equation of energy ;E=MC^2 indicates that only the particles of light can move at the speed of light.
Hence M in the Einstein equation is the summation of light massiveness
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