Question

A particle of mass M is moving in the positive x direction with speed v. It spontaneously decays into 2 photons, with the original particle disappearing in the process. One photon has energy 233 MeV and moves in the positive x direction, and the other photon has energy 21 MeV and moves in the negative x direction. (5) (a) Draw a picture of this process. What is the total relativistic energy of the particle before its decay

Answer 1

Mass of the particle = M

Speed of travel = v

Energy of one photon after the decay which moves in the positive x direction = 233 MeV

Energy of second photon after the decay which moves in the negative x direction = 21 MeV

Therefore, the total energy after the decay is = 233 + 21

= 254 MeV

So by the law of conservation of energy, we have :

Total energy before the decay = total energy after decay

So, the total relativistic energy of the particle before its decay = 254 MeV