The time-independent Schrödinger equation for one particle in one dimension can be written as − − ℏ ℏ 2 2 m d 2 d x 2 Ψ Ψ ( x ) + V ( x ) Ψ Ψ ( x ) = E Ψ Ψ ( x ) or d 2 d x 2 Ψ Ψ ( x ) = 2 m ℏ ℏ 2 ( V ( x ) − − E ) Ψ Ψ ( x ) ≡ ≡ 2 m ℏ ℏ 2 M ( x ) Ψ Ψ ( x ) , where