How does Michael Frayn use imagery in Copenhagen?

Frayn uses descriptive imagery to portray the world before the war. When Margrethe and Bohr discuss his work before the war, and the way they spent their summers together and going on vacation with Margrethe and their children. The memories illustrate an idyllic picture that allows coexisting and happiness, regardless of nationality. This image, however, changes over time, and Heisenberg ceases being a friend and becomes an enemy.