BOXED IN A poem by Dr. James D. Livingston Put an electron in a box And walls constrain its 's Its wavelength has to match the width So energy must quantize The 's are limited to sines The k's controlled by L Rules are strict for electrons in A deep potential well Outside the well, the rules are loose And waves can travel free But waves are bound inside the box If low in energy If V 's the depth of the well you're in The moral's clear to see If you want your waves to wash the world Your E must exceed your V !

(image from HyperPhysics)