A detector shows evidence of the creation of an electron...

A detector shows evidence of the creation of an electron positron pair. If the tracks of the particles indicate that each one has a kinetic energy of $0.22 \mathrm{MeV}$, what is the energy of the photon that created the two particles?

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Key Concepts

Pair Production

This is a quantum process in which a high-energy photon is converted into a particle-antiparticle pair, such as an electron and a positron. The process can only occur if the photon has enough energy to provide the combined rest mass energy of the two particles, and it typically requires the presence of a nearby nucleus to conserve momentum.

Rest Mass Energy

Rest mass energy is the intrinsic energy associated with a particle's mass, calculated using Einstein's equation E=mc². For electrons and positrons, this energy is approximately 0.511 MeV each, setting the minimal energy required for their formation during pair production.

Energy Conservation

Energy conservation is a fundamental physical principle stating that the total energy of a closed system remains constant over time. In pair production, the energy of the incoming photon is completely converted into the rest mass energies of the electron and positron plus any additional kinetic energy they acquire.

Kinetic Energy

Kinetic energy is the energy that particles possess due to their motion. In the context of pair production, any photon energy that exceeds the sum of the rest mass energies of the electron and positron appears as kinetic energy, which the particles exhibit as they move after creation.

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