5.B.: Nodes and DeBroglie's principle
The stationary states, or eigenstates, for a particle moving between two walls (introduced in the previous section).
Nodes are positions where the wave function is equal to zero. The more nodes, the shorter the wave length. DeBroglie's principle states that energy increases with more nodes, or shorter wave length. For a particle bouncing between two wall, there are n - 1 nodes in the wave functions of eigenstate n.
More nodes means shorter wave length and higher energy.