$A$ gamma ray photon creates an electron-positron pair. If the rest mass energy of an electron is $0.5 \, MeV$ and the total $K.E.$ of the electron-positron pair is $0.78 \, MeV$,then the energy of the gamma ray photon must be .......... $MeV$.

  • A
    $0.78$
  • B
    $1.78$
  • C
    $1.28$
  • D
    $0.28$

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