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k-SPACE

The wavenumber of a wave has a special significance in both classical and quantum physics. Because waves are quantized (they can only occur in ``packets'' of energy and momentum ) we are often in the position of asking what possible values k can have, and counting the number of allowed k values. From this procedure arises the notion of `` k-space'' and the density of states in k-space, which may seem rather exotic on the first encounter but with which every physicist ultimately becomes intimately familiar.

The following arguments apply to any sort of wave (or wavefunction) that is confined to a finite region and constrained to have nodes at the boundaries.