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According to the equation E=hv, does a photon have mass? This because it has energy, not because it is moving at the speed of light,
- Richard Ong (age 14)
Winston-Salem, NC, USA
As we've noted many times here, a photon has effective mass m= E/c2
. That's the m that appears in the momentum-velocity relation p
and as a source term for gravity. It doesn't have "invariant mass", i.e. rest-mass sqrt(E2
), because, since it travels at c, E=pc.
(published on 12/19/11)
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