Electron Undergoing Annihilation

[Jacob87411]

A 5MeV electron undergoes annihilation with a positron that is at rest, producing two photons. One of the photons travels in the direction of the incident electron. Calculate the energy of each photon.

So the 5 MeV electron undergoes annihilation with a positron and from that 2 separate photons are formed. The energy of both photons should equal back up to the 5 MeV correct? Also one of the photons travels back the same way the electron came but I am not clear on how to use that piece of info.

 

[SpaceTiger]

So the 5 MeV electron undergoes annihilation with a positron and from that 2 separate photons are formed. The energy of both photons should equal back up to the 5 MeV correct?

Don't forget to include the rest energy of the stationary particle. Is 5 MeV is the total energy or kinetic energy of the other one?

Also one of the photons travels back the same way the electron came but I am not clear on how to use that piece of info.

You need to conserve both momentum (a vector) and energy (a scalar).

 

[Jacob87411]

Ah, right..momentum is conserved. So the particles will be a sum of the 5MeV and the rest energy of that positron.