rest mass of photon is 0, v=c, applying it in einstein's equation for mass, we get 0/0 (zero divided by zero). WHat is its value then?
2006-09-08 16:06:37 · 10 answers · asked by Sachin 2 in Science & Mathematics ➔ Physics
Photons are supposed to be massless while at rest (which is a fun thing to do, since they can only exist traveling at the speed of light).
So the energy of a photon is a function of its frequency. You multiply the frequency by Planck's constant, and you get the energy. From that, you can derive a virtual mass if you so choose, as at that scale, it is all pretty much the same.
So, gamma radiation would have more "mass" than visible light photon, which would have more "mass" than radio wave photons...
2006-09-08 16:14:10 · answer #1 · answered by Vincent G 7 · 1⤊ 0⤋
Photons do not have mass, however they do (by the nature of having energy) possess momentum.
The energy of a photon is given as,
E = hv
where E is the energy, h is plank's constant, and v is the frequency of light.
Everyone is familiar with the equation,
E = mc^2
ans think that they can relate a photon's energy to its mass with some simple algebra,
m = E / c^2
However, this is not the case. The "m" in E = mc^2 refers to the particles REST MASS. A photon's rest mass is ZERO.
There is an often omitted part of the equation which relates the energy a massless particle possesses to its momentum,
E = mc^2 + pc
We already know that mc^2 = 0,
so we are left with E = pc
where E is the energy, p is the momentum, and c is the speed of light in a vacuum.
Setting the energy of a photon equal to the this gives us,
hv = pc
So to solve for the momentum (p),
p = hv / c
2006-09-09 01:13:23 · answer #2 · answered by mrjeffy321 7 · 0⤊ 0⤋
A photon is a quantum of energy. While it may be able to behave like a "particle", it is essentially massless. You need to use deBroglie's formula in order to come up with an "equivalent" mass which is not the same as the mass associated with classical objects.
2006-09-08 23:23:33 · answer #3 · answered by eriurana 3 · 1⤊ 0⤋
A photon has no mass or at least no "invariant mass" The old definition of mass was "relativistic mass" where m = E/c^2.
2006-09-08 23:13:21 · answer #4 · answered by Andy S 6 · 0⤊ 0⤋
To my understanding, photons do have mass (which is why there is a gravitational lens effect), but no matter what speed a photon is traveling, its mass is too low to be measurable by current methods.
2006-09-08 23:24:35 · answer #5 · answered by JBarleycorn 3 · 0⤊ 1⤋
42
2006-09-08 23:08:17 · answer #6 · answered by Bill M 2 · 0⤊ 1⤋
http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/photon_mass.html
I am not a physics person. I am a chem person, but apparently (from this article) there are different definitions of mass, and a photon is believed to have a mass extremely near zero, but a mass nevertheless
2006-09-08 23:15:38 · answer #7 · answered by applejacks 3 · 0⤊ 2⤋
could you apply it to E = mc2
m = E/c2
in Calculus is something gets samller and smaller(essentially zero but never reaches zero), it is just ignored
i.e. 1/0.00000000000001, pretty much comes out as 1/0 but equals 1
2006-09-08 23:18:35 · answer #8 · answered by merakesh_one 1 · 0⤊ 1⤋
Man I don't even know why I'm in this section. Half this stuff I don't even know. But i did memorize the actual speed of light: 2.99792458*10^8. Haha. Pysichs text book. Anyway completely irrelevant to your question so forgive me.
2006-09-08 23:12:14 · answer #9 · answered by Romaneasca 3 · 0⤊ 1⤋
Pie the 3.526 to the 8th power.
2006-09-08 23:07:54 · answer #10 · answered by scraps 2 · 0⤊ 1⤋