Question

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-position pair is `0.78 MeV`, then the energy of the gamma ray photon must be.
A. `0.28MeV`
B. `0.78MeV`
C. `1.28MeV`
D. `1.78MeV`

Answer 1

Correct Answer - D
`gamma rarr e^(+) +e^(-)`
Energy of photon `= 2xx0.51 + 0.78 = 1.78MeV`