Hendrik Anthony Kramers††See Introduction to Part II, p. [116].

Franco Strocchi

Niels Henrik David Bohr

Peter Millington

Franklin de Lima Marquezino, Renato Portugal, Carlile Lavor

S. Rajasekar, R. Velusamy

The WKB approximation is a physically intuitive method and makes many connections with intuition about waves and classical mechanics as well as with results from the early days of quantum theory as it leads to the Bohr quantization condition. The WKB method is due to Gregor Wentzel, Hendrik Anthony Kramers and Leon Nicolas Brillouin. The method is applicable for slowly varying potentials, that is, the potentials that change not more than a few wavelengths. The WKB approximation is a physically intuitive method and makes many connections with intuition about waves and classical mechanics as well as with results from the early days of quantum theory as it leads to the Bohr quantization condition. The Schrödinger equation is solved to find the penetration of a square potential barrier. The WKB method is applied to obtain a transmission coefficient for penetration through a barrier.

Philip Ball

Philip Ball peers into the quantum past, and uncovers a little-known paper published by Niels Bohr, Hendrik Kramers and John Slater in 1924, that proposed that the first law of thermodynamics may no longer hold firm. Their idea turned out to be wrong, but in interesting and provocative ways, and it demonstrates the intense turmoil in physics on the brink of quantum mechanics.