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Question

Question: A gamma ray photon creates an electron- positron pair. If the rest mass energy of an electron is 0.5...

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- positron pair is 0.78 MeV, then the energy of the gamma ray photon must be.

A

0.78 MeV

B

1.78 MeV

C

1.28 MeV

D

0.28 MeV

Answer

1.78 MeV

Explanation

Solution

Energy of γ-ray photon =0.5+0.5+0.78=1.786muMeV0.5 + 0.5 + 0.78 = 1.78\mspace{6mu} MeV.