In pair annihilation, an electron and a positron destroy each other to produce gamma radiation. How is the momentum conserved ?
In pair annihilation, an electron and a positron destroy each other to produce gamma radiation. How is the momentum conserved ?
When an electron and positron move towards each other with equal speeds, their total momentum is, $m v \hat{i}+m v(-\hat{i})=m v \hat{i}-m v \hat{i}=\overrightarrow{0}$
When above particles annihilate (merge), we get emission of two $\gamma$-ray photons, moving in opposite directions whose total momentum is $\frac{h}{\lambda} \hat{i}+\frac{h}{\lambda}(-\hat{i})=\overrightarrow{0}$
Thus, total momentum remains constant, before and after annihilation. Hence momentum gets conserved.
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