Question

A photon (in a vacuum) travels at the speed of light with energy E. What is the minimum energy required for the photon to convert into an electron-positron pair? (The mass of the electron and the positron are both the mass of an electron).

Answer 1

The energy of the photon must be equal to the mass of both electron and positron

From mass energy relation E = m_e c²

m_e = mass of electron = 9.31 * 10^ (-31) kg

c = velocity of light = 3 * 10^8 m/s

E = 0.51 MeV

For the photon to produce both electron and positron the energy of the photon must be equal to double the above value, as electron and positron have same mass

Hence the required energy for photon is 1.02 MeV

Sorry for wrong answer

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