Author and playwright Michael Frayn talks with Steve Paulson about his play “Copenhagen” and the dramatic meeting between physicists Neils Bohr and Werner Heisenberg in 1941. At issue is the degree to which Heisenberg was spying for the Nazis and his role in the development of a German atom bomb. And we hear clips from the play. Frayn and Paulson go on to discuss Frayn’s novel “Spies” in which two boys come to suspect during the Second World War that the mother of one of them is a German spy.