1D problems

Time-independent Schroedinger equation:

(-ħ2/(2m))∂2ψ(x)/∂x2 + U(x)ψ(x)  - Eψ(x) = 0

2ψ(x)/∂x2 + k(x)2ψ(x) = 0,

with

 k(x)2 = 2m(E - U(x))/ħ2

The solutions are stationary states.

Infinite square well:  k2 is independent of x inside the well, ψ(x) is zero outside the well.

2ψ(x)/∂x2 + k2ψ(x) = 0

Solutions:  ψn(x) = (2/L)1/2sin(nπx/L),   En = n2π2ħ2/(2mL2).