Find the energy of an incoming photon which strikes a statio

Find the energy of an incoming photon which strikes a stationary electron and produces an electron/positron pair.

The rest mass energy of an electron is 511.875 keV.

The rest mass of a positron (anti electron) is also same energy i.e., 511.875 keV.

So, you need at least the energies of the rest masses of the particles i.e., 511.875 keV +511.875 keV = 1023.75 keV or 1.02375 MeV.

Therefore minimum energy of the photon for pair production is 1.02375 MeV

Energy of the photon for pair production is greater than or equal to 1.02375 MeV

Note :

Rest energy of electron E= mc ²

Where m = rest mass of electron = 9.1x10 ^-31 kg

So,E = (9.1 x10 ^-31 )(3 x10 ⁸) ²

= 8.19 x 10 ^-14 J

=[(8.19 x10 ^-14 )/(1.6 x10 ^-13)]MeV

= 0.511875 MeV

= 511.875 keV