Wentzel’s lesson in humility

The WKB approximation used in quantum mechanics doesn’t often draw attention, but it appears in John Knox’s letter (Physics Today, September 2005, page 17 ). Knox properly identifies Gregor Wentzel as the “W” in that acronym, thereby bringing back memories of a period in 1948 when I took a quantum mechanics course taught by Wentzel at the University of Chicago. He was a great teacher who was known for his humility and self-effacement. I remember his first reference to WKB when he wrote on the blackboard, “BKW,” clearly announced the names “Brillouin” and “Kramers,” and almost as an aside, mumbled the “Wentzel.”