Emission of a photon

andrien

if you don't use the definition of relativistic mass then,right.Otherwise both are same.Energy is time component of four momentum and mass is invariant,so they are really different. if one avoids the notion of relativistic mass which is already abandoned then of course it is wrong.But that is just not what I say.It is a matter of definition.

K^2

Fact that use of m as symbol for relativistic mass is outdated was the whole point of mfd's comment, and the reason for your reply to denisfl8 being at very least incomplete.

Mass, without qualifier, is assumed to be invariant mass. If you want to talk about relativistic mass, you should qualify that for clarity. Were you to reply that, "Energy is equivalent to relativistic mass," there would be no complaint.

andrien

Oh,sorry for that.