(6-5) ① Since the particle can’t be beyond the infinite wall, it follows that ψ(x) = 0 in those regions. Taking Erwin’s extra requirement into account, this means it must also be true that ψ = 0 at the wall, where x = 0, otherwise there would be a discontinuity. How does this let us simplify our expression for ψ(x)?
② In the same way, it must be true that ψ(x) = 0 at the other wall, where x = L. See if you can build in this constraint too, and derive an expression for a wavefunction.
③ Sketch the form of some of the possible wavefunctions you have discovered.