for Physics II
Wave mechanics supplied the explanation for the tunnel effect. This effect permits that a quantum particle overcomes (is tunneling through) obstacles (potentials), which are impenetrable for classical particles (see simulation 6/9)).
The tunneling through effect, for example, explains the alpha-decay of radioactive nuclei.
It also serves as the foundation of the scanning electron microscope: According to the ideas of quantum mechanics the distribution of electrons in a solid body does not stop abruptly at the surface, but forms a cloud above it. If a metal point comes close to a conducting surface without touching it, electricity will flow (tunnel electricity) provided some voltage runs through.