A question very similar to the one I'm asking about has been asked before on here, but I'm uncertain about the reasoning behind the answer, and really need some clarification, so if anyone could help me that'd be grand.
This question is from a past exam paper.
What I understood from books that I have read, and what the answer to this (Quick question on sketching wavefunction in well) suggests, is that the wavelength and the amplitude of the wavefunction are smaller when the potential is lower.
I'm fine with the wavelength part, that makes sense to me due to the second derivative of the wavefunction being greater when E - V is greater, but it is the amplitude that I am uncertain about, and in fact that examiner's solution to this question says that the amplitude is greater when the potential is lower.
So the argument that I have seen numerous times is that if E - V is lower in a certain region then the kinetic energy in that region is smaller, so the particle spends more time in that region, leading to a higher probability density, and hence a greater amplitude of the wavefunction.
But is this not essentially a classical argument that breaks down when you have a eigenfunction which doesn't represent a physically realisable state? I mean, for the case of the infinite well there would also then be points where the particle cannot exist, and this clearly doesn't represent a physical situation?
If you attack this problem by first order perturbation theory then the wavefunction does seem to tend towards having a greater amplitude when the potential is lower, rather than the other way round.
So, what is the correct answer to this?