Does wavefunction reach its largest peak near(not in) the classical forbidden region?

As we can see in the picture in this website:

http://ctz116.ust.hk/xyli2/images/animation/quchem73.html

It's strange that the bound state wavefunction always reach its largest peak near the boundary of its classically forbidden region(not in the region). Is it true that this phenomenom holds for all bound state wavefunction?

I think that the reflected wave may interfere with the original one, thus creating the peak near the forbidden region.But I can't explain why it is the largest peak or there is no peak inside the classically forbidden region,Thanks for your attention.

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1 Answer

Yes, the wavefunction will peak near the boundary of the forbidden region and this effect will increase at higher energy levels. In the limit of very high energy levels the quantum harmonic oscillator must reproduce the classical result and a classical harmonic oscillator will more likely be found near the endpoints of its motion since that is when it is moving much slower than in the center where it has maximum velocity and maximum kinetic energy.

A quote from Wikipedia:

Note that the ground state probability density is concentrated at the origin. This means the particle spends most of its time at the bottom of the potential well, as we would expect for a state with little energy. As the energy increases, the probability density becomes concentrated at the classical "turning points", where the state's energy coincides with the potential energy. This is consistent with the classical harmonic oscillator, in which the particle spends most of its time (and is therefore most likely to be found) at the turning points, where it is the slowest. The correspondence principle is thus satisfied

The Wikipedia article also has the following animated images showing the wavefunction for eigenstates as well as animations for wavefunctions of states that are not eigenstates that begin to approximate the classical behavior of moving back and forth from one limit state to the other.

Some trajectories of a harmonic oscillator according to Newton's laws of classical mechanics (A-B), and according to the Schrödinger equation of quantum mechanics (C-H). In (A-B), the particle (represented as a ball attached to a spring) oscillates back and forth. In (C-H), some solutions to the Schrödinger Equation are shown, where the horizontal axis is position, and the vertical axis is the real part (blue) or imaginary part (red) of the wavefunction. (C,D,E,F), but not (G,H), are energy eigenstates. (H) is a coherent state, a quantum state which approximates the classical trajectory.

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