Chapter 15, Problem 15.90P

(a)

To determine

Show that in the process $\gamma \to {\text{e}}^{+}+{\text{e}}^{-}$ isolated photon cannot convert to an electron-positron pair.

(b)

To determine

Show that the minimum energy to induce the reaction is approximately $2m_e{c}^2$ , provided the mass of the nucleus in the process $\gamma +\text{nuclues}\to {\text{e}}^{+}+{\text{e}}^{-}+\text{nuclues}$ must be greater than that of electron and positron.