What is the amount of energy given off when an electron and a positron annihilate?

Question

What is the amount of energy given off when an electron and a positron anhilalate?
Asked by: Bill Devenport

Answer

Using 9 x 10^-31 Kg. as the mass of each particle, and knowing that their combined mass will be totally converted to energy, you can use Einstein's famous E = mc² (where c = the speed of light in vacuum = 3 x 10⁸ m/sec) to determine the total energy output of the electron/positron annihilation:

E = (mass of electron + mass of positron) x (speed of light in m/sec)²

E = 2 x (9 x 10^-31)kg x (9 x 10¹⁶)m²/sec²

E = 1.6 x 10^-13 kg m²/sec² = 1.6 x 10^-13 Joules
Answered by: Paul Walorski, B.A. Physics, Part-time Physics Instructor

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