Does light have mass? Also, is it a partical or a wave?
Does light have mass?
| Neilos wrote: |
| Also, is it a partical or a wave? |
No.
Sometimes it is helpful for us to think of it one way or another... it lets us understand it, and we can use these models of what light is to predict things.
That doesn't mean that it actually is either though. Really, it's something different from both, probably something that us humans have nothing to compare with.
Light is(has?) energy.
Since E = mc^2
I would say light has a mass.
Since E = mc^2
I would say light has a mass.
| TomS wrote: |
| Light is(has?) energy.
Since E = mc^2 I would say light has a mass. |
Wrong.
This question has been asked and answered so many times I may do a FAQ on it. Until then I'll simply point you to an article which explains the basics.
http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/photon_mass.html
Is it correct that the equivalent for E = nc^2 is E = pc for light? And p is the momentum of the light particle? But all along, in classical mechanics, I have come across momentum in terms of mass and velocity as a product of the two. So how is this possible in the case of light? So in terms of what is momentum defined for light?
| _AVG_ wrote: |
| Is it correct that the equivalent for E = nc^2 is E = pc for light? And p is the momentum of the light particle? But all along, in classical mechanics, I have come across momentum in terms of mass and velocity as a product of the two. So how is this possible in the case of light? So in terms of what is momentum defined for light? |
I could answer this for you, and I will if you REALLY need me to. I'd rather you did a bit of reading of your own, however, therefore I'll leave this for a few days and see if you can answer your own question.
Is it this?
I found that if you equate both equations E = pc and E = hf, you get pc = hf
pc = hf
=> p = hf/c BUT c/f = wavelength
therefore, p = h/wavelength
I found that if you equate both equations E = pc and E = hf, you get pc = hf
pc = hf
=> p = hf/c BUT c/f = wavelength
therefore, p = h/wavelength
| _AVG_ wrote: |
| Is it this?
I found that if you equate both equations E = pc and E = hf, you get pc = hf pc = hf => p = hf/c BUT c/f = wavelength therefore, p = h/wavelength |
Exactly - light has momentum but no mass.
| Bikerman wrote: | ||
Exactly - light has momentum but no mass. |
But momentum = mv, and if m (photon mass) = 0, then light does NOT have momentum!
| Dennise wrote: | ||||
But momentum = mv, and if m (photon mass) = 0, then light does NOT have momentum! |
Yep - true if you apply Newtonian theory - but in relativistic theory it does indeed have momentum. That is actually key to the observations that confirmed (or at least strongly supported) Einstein's model.
http://en.wikipedia.org/wiki/Photon
simple answer yes....
| sum12nv wrote: |
| simple answer yes.... |
No, the simple answer is no...not to the best of our current knowledge.
thanks for the info peeps! very interesting
Light is a particle and wave at the same time.
http://nobelprize.org/nobel_prizes/physics/articles/ekspong/
http://nobelprize.org/nobel_prizes/physics/articles/ekspong/
From my understanding (most likely wrong)
Light can and is influenced by gravity (such as being "bent" around planets, and being "trapped" inside black holes). For light to be physically influenced, it therefore must have a mass.
Once again, I am most likely wrong, but would like some more info upon the matter in a really simple way. I am not the quickest :S
Light can and is influenced by gravity (such as being "bent" around planets, and being "trapped" inside black holes). For light to be physically influenced, it therefore must have a mass.
Once again, I am most likely wrong, but would like some more info upon the matter in a really simple way. I am not the quickest :S
| rayz0r wrote: |
|
Light can and is influenced by gravity (such as being "bent" around planets, and being "trapped" inside black holes). For light to be physically influenced, it therefore must have a mass. |
No, read up on Einstein... Light bends, not because it has mass, but because the space it travels through is bent by gravity; the light is taking a straight path over a curved surface.
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