Q. A positron is a particle of "antimatter"; it has the same mass as an electron (9e-31 kg), but its charge is positive instead of negative. At research facilities such as Cornell Electron Positron Storage Ring at Cornell University in New York, high energy beams of positrons can be produced.

While a positron encounters an electron, the two particles annihilate each other, and produce two high energy photons (gamma rays), which travel away from each other.

Assume that a positron travelling at a speed of 0.95 c collides head on with an electron travelling at the same speed.

What is the sum of energies of the two photons which are produced when the positron and the electron annihilate?
Sum of photon energies = J?