A γ ray photon produces an electron positron pair. If the rest mass energy of electron is 0.51 MeV and the total kinetic energy of electron - positron pair is 0.78 MeV then the energy of ray photon in MeV is :
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Question

A γ ray photon produces an electron positron pair. If the rest mass energy of electron is 0.51 MeV and the total kinetic energy of electron - positron pair is 0.78 MeV then the energy of ray photon in MeV is :

Options

G1 Physics · Accepted Answer

Pair production must supply the two rest-mass energies plus kinetic energy. Minimum rest-mass energy = 2(0.51) = 1.02 MeV. Adding the given total kinetic energy 0.78 MeV gives photon energy 1.80 MeV. Correct answer: B.