How exactly wud u do this

[EIRE2003]

gamma ray -> positron + electron


calculate the min freq of the gamma ray photon required for this reaction occur.

the reverse of the above reaction is pair annihiation. Write a reaction that represents pain annhiliation.
I thought this would be positron + electron -> gamma ray

[cookiemonster]

Assume that after the reaction, both the positron and electron are at rest. What is the energy involved in the positron-electron system?

This energy will be the same as on the left-hand side of the equation, except gamma rays have energy based on frequency. Set the two equal and solve for frequency.

cookiemonster