# Mass of a Photon

• Start date
• #1
50
0
If the energy of a photon: Ephoton = hν, where h = Planck's constant,
and E = mc2, then does hv = mc2

And if so, if c=vλ: Ephoton = hc/λ = mc2

Thus mass: m = h/λc ?

• #2
Khashishi
2,815
493
##E=mc^2## only applies to massive particles at rest, not photons. You need to use the full equation which is
##E^2 = m^2c^4 + p^2 c^2##

• #3
50
0
##E=mc^2## only applies to massive particles at rest, not photons. You need to use the full equation which is
##E^2 = m^2c^4 + p^2 c^2##
So what is the momentum of photons since gravitation is applied?

• #4
Khashishi
2,815
493
Set m=0 and you get ##E = pc##. You can solve for the momentum of the photon.

• #5
50
0
Set m=0 and you get ##E = pc##. You can solve for the momentum of the photon.
Ah. Thank you

• #6
ZapperZ
Staff Emeritus
35,977
4,683
Please note that this has been covered and answered in one of our FAQ.

Zz.

Last edited:

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