Wave function

Narrow the potential barrier

Note that the height of the incoming wave function has nothing to do with the height of the potential barrier. The wave function has no units, while the potential barrier has units of energy.

As the wave function hits the potential barrier, the amplitude is suppressed exponentially inside the barrier, and only a small amplitude is transmitted on the right of the barrier. Small amplitude implies a small probability, and the particle has a small chance of tunneling through the potential barrier.

Decreasepotential barrier

Widen the potential barrier

Potential barrier

Quantum Tunneling

Increasepotential barrier