physics (special relativity)

A single photon in empty space is transformed into an electron and a positron, each with rest mass m(e).

(a) show that the folowing process is dynamically impossible.
(b) Explain in detail how this process can be made possible
(c) for part b what would be the minimum photon energy required for this to happen?

Show all steps in calculation

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  1. Gamma rays of sufficient energy can create a positron and an electron, if the photon energy exceed 2 m c^2.

    This can only happen in the presence of another mass , which is needed to allow both energy and momentum to be conserved. Sone of the original photon momentum has to be transferred to another mass.

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