Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: CZARCAR on 27/11/2011 13:15:15

i dont get it. if mass=0, then photon has no energy?

That's only the correct equation when you're calculating the energy of something that is sitting still. Light always moves at light speed, so the correct equation in that case is:
E^{2}=(mc^{2})^{2}+(pc)^{2},
where p is momentum. A photon has no mass (m=0), but it has momentum, (p≠0). Therefore, it has energy.

thanx