I have nothing more to add to my previous answer.
ttp://www.jiskha.com/display.cgi?id=1307558664
A single photon in empty space is converted into an positron and an electron, each with rest mass 511Mev.
(a) show this transformation is not possible (dynamaically).
(b)How could this transformation be made posible.
(c)what is the minimum photon energy required to enable the process in part b.
please show working
2 answers
There should have been an "h" at the beginning of the link I posted.
For a discussion of why a third body is required for pair creation, see
http://books.google.com/books?id=GgFjLiZDOk8C&pg=PA118&lpg=PA118&dq=electron+positron+creation+third+body&source=bl&ots=w0H9QEXfMC&sig=_0Cl-HfHIyIdgCE5xlKSMCqckog&hl=en&ei=oUf1TcTpD-XRiAKzl5mGBw&sa=X&oi=book_result&ct=result&resnum=3&ved=0CCIQ6AEwAg#v=onepage&q=electron%20positron%20creation%20third%20body&f=false
For a discussion of why a third body is required for pair creation, see
http://books.google.com/books?id=GgFjLiZDOk8C&pg=PA118&lpg=PA118&dq=electron+positron+creation+third+body&source=bl&ots=w0H9QEXfMC&sig=_0Cl-HfHIyIdgCE5xlKSMCqckog&hl=en&ei=oUf1TcTpD-XRiAKzl5mGBw&sa=X&oi=book_result&ct=result&resnum=3&ved=0CCIQ6AEwAg#v=onepage&q=electron%20positron%20creation%20third%20body&f=false