Quantum tunnelling

Quantum tunneling is a phenomenon where particles like electrons can pass through potential energy barriers that would be insurmountable according to classical mechanics. This occurs due to the wave nature of matter and quantum indeterminacy, allowing a small part of the wavefunction to appear outside the barrier, representing a probability for tunneling.

The probability of a particle tunneling through a barrier decreases exponentially with the barrier height, width, and the particle's mass. This means that tunneling is most prominent in low-mass particles such as electrons, which can tunnel through atomically narrow barriers. However, tunneling has also been observed with protons and even atoms.

Tunneling has practical applications and explains physical effects with particles. For instance, it is used to explain phenomena like alpha decay in nuclear physics and the operation of tunnel diodes in electronics.