Classical and quantum mechanics are two very different theories, each one
describing the world within its own range of validity. According to Planck's version of the correspondence principle, classical mechanics is recovered when the limit in which Planck's constant h goes to zero is taken, while within Bohr's version the limit of large quantum
numbers is taken. However, despite what suggested by many textbooks, the relation between
the two theories is much more complex to state and understand. Here we deal with this issue by
analysing some key examples. Implications for quantum mechanics teaching at undergraduate
level are carefully discussed.
Adele Naddeo Prof. Antonino Drago (Dipartimento di Fisica, Università di Napoli "Federico II") Dr Marco Di Mauro (Dipartimento di Matemtica, Università di Salerno)