Simple question about photons turning into electorn positron pairs.

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SUMMARY

A photon in free space cannot transform into an electron-positron pair due to the conservation of energy and momentum. The equation E^2 - P^2 = 0 applies to photons, indicating that their energy and momentum are balanced. However, for an electron-positron pair, the combined energy and momentum must satisfy the inequality (E_1 + E_2)^2 - ({\vec p}_1 + {\vec p}_2)^2 > 0, which cannot be achieved in a vacuum without additional particles to conserve momentum.

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cpfoxhunt
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Homework Statement



This is a really easy one, goodness only knows why I can't think of how to do it, here goes

" Explain why a photon in free space cannot turn into an electron-positron pair."


Homework Equations



I assume E^2- P^2 = 0 will be of some help

The Attempt at a Solution



I'm stuck - why on Earth shouldn't it if it has sufficient energy to provide the necessary rest masses? Why don't photons do this all the time?

Cheers
Cpfoxhunt
 
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E^2-p^2=0 for a photon, but it must be positive for an electron-positron pair.
That is (E_1+E_2)^2-({\vec p}_1+{\vec p}_2)^2>0.
 
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