Degeneracy occurs in general whenever a system is labeled by two or more
quantum numbers; as we have seen in the above calculation, different combinations
of quantum numbers often can give the same value of the energy. The number
of different quantum numbers required by a given physical problem turns out
to be exactly equal to the number of dimensions in which the problem is
being solved—one-dimensional problems need only one quantum number, twodimensional
problems need two, and so forth. When we get to three dimensions,
as in Problem 19 at the end of this chapter and especially in the hydrogen atom in
Chapter 7, we find that the effects of degeneracy become more significant; in the
case of atomic physics, the degeneracy is a major contributor to the structure and
properties of atoms.