- #1
Hevonen
- 54
- 0
[SOLVED] Annihilation, perhaps a defination problem
Problem:
An electron and an anti-electron undergo mutual annihilation.
Which of the following does not have to be conserved?
A. Electric charge
B. Kinetic energy
C. Lepton number
D. Momentum
Attempt to question:
The answer is B but I why not also d. I would consider that the mass of photon is zero. So in both B and D, kinetic energy and momentum are perhaps zero. Problem is: it is impossible to divide by zero. Therefore, this problem seems to a definatition problem. It must be that momentum conserves but why? What is the assumption in the theory?
Thank you for your answers!
Problem:
An electron and an anti-electron undergo mutual annihilation.
Which of the following does not have to be conserved?
A. Electric charge
B. Kinetic energy
C. Lepton number
D. Momentum
Attempt to question:
The answer is B but I why not also d. I would consider that the mass of photon is zero. So in both B and D, kinetic energy and momentum are perhaps zero. Problem is: it is impossible to divide by zero. Therefore, this problem seems to a definatition problem. It must be that momentum conserves but why? What is the assumption in the theory?
Thank you for your answers!