Generation of Particles
One of the consequences of the equivalence of energy and mass is that in a collision of two particles, occurring at a very high energy E, new electromagnetic waves (radiation), as well as new particles can be produced:
The formation of new particles by such a collision and in additional "energy" in the form of electromagnetic radiation underlie the most important physical principles: the conservation of momentum and the conservation of energy. The conservation of momentum means that the vector addition of the moments of all the components has to be exactly the same before and after the collision.
The same is also valid for the total energy E, thus the total energy after the collision is divided in many parts, corresponding to the outgoing waves and particles with mass m1, m2, ..., m5 and the radiation quanta hν1, hν2, ..., hν4:
E = m1c2 + m2c2 + m3c2 + m4c2 + m5c2 + hν1 + hν2 + hν3 + hν4