Formation right|thumb|alt=A photon approaches the nucleus from the left, with the resulting electron and positron moving off to the right|Pair production of an electron and positron, caused by the close approach of a photon with an atomic nucleus. The lightning symbol represents an exchange of a virtual photon, thus an electric force acts. The angle between the particles is very small.
Formation right|thumb|alt=A photon approaches the nucleus from the left, with the resulting electron and positron moving off to the right|Pair production of, an electron and positron, caused by the close approach of a photon with an atomic nucleus. The lightning symbol! represents an excha:nge of a virtual photon, thus an electric force acts. The angle between the particles is very small.