Basic Ideas of Quantum Mechanics
THE TERMINOLOGY in this branch of physics is still strongly conditioned by its recent origin and carries an awkwardness at times resembling confusion. This makes a few introductory comments for the purpose of general orientation seem appropriate.
There is no consensus even with respect to the name of the subject we are about to treat. Sometimes it is called matrix mechanics, sometimes wave mechanics, and now more commonly quantum mechanics. Each of these names has a good historical warrant, and it is illuminating to recall briefly how they came to be adopted.
In 1924 Heisenberg discovered a calculus which allowed some of the properties of atomic systems to be calculated with striking success, and because this calculus involved matrices as major mathematical tools, the first name arose.
A little more than one year later, Schrödinger published three amazing papers in which he derived the same results by what appeared to be a totally different method of calculation. He solved an equation very much like the wave equation of classical physics and thus produced a theory which formed an extension (though with radical modifications) of the ideas of de Broglie. This complex of theories was called wave mechanics. It is well to note at once that the solutions of Schrödinger's equation are wavelike only for the simplest physical systems, taking on in general a rather complicated form which bears little resemblance to ordinary waves in space. The name "wave mechanics" is therefore not very descriptive of what goes on in the subject it designates, and the steadfast adherence to it on the part of some physicists has, perhaps, injected into an already difficult situation a misleading