A proton is bound in a square well of width 4.0 fm = 4.0 x 10-15 m.

Question:

A proton is bound in a square well of width 4.0 fm = 4.0 x 10-15 m. The depth of the well is six times the ground-level energy E= of the corresponding infinite well. If the proton makes a transition from the level with energy E, to the level with energy E, by absorbing a photon, find the wavelength of the photon.