A `5 xx 10^(-4) Å` photon produces an electron-positron pair in the vincinity of a heavy nucleus. Rest energy of electron is `0.511 MeV`. sIf they have the same kinetic energies, the energy of each paricles is nearly

Options

A. `1.2 MeV`
B. `12 MeV`
C. `120MeV`
D. `1200MeV`

Answer

b

Explanation

If the kinetic energy of each particle is k, then
`2+2(0.511 MeV)=(hc)/(lambda)=(12.4xx10^(-3) MeV Å)/(5 xx 10^(-4)Å) =24.8 MeV`
`rArr k=(24.8 -1.022)/(2)=11.9 MeV` .