An electron is considered as a wave FUNCTION. The probability of finding an electron is directly proportional to the square of the amplitude of the wave function. When the wave function of an electron encounters a POTENTIAL barrier, its amplitude decreases exponentially. For a narrow barrier, the wave amplitude may not become zero after the electron passes through the barrier. HENCE, there is a non-zero probability that the electron will be FOUND beyond the barrier. This process is called quantum tunneling.

An electron is considered as a wave function. The probability of finding an electron is directly proportional to the square of the amplitude of the wave function. When the wave function of an electron encounters a potential barrier, its amplitude decreases exponentially. For a narrow barrier, the wave amplitude may not become zero after the electron passes through the barrier. Hence, there is a non-zero probability that the electron will be found beyond the barrier. This process is called quantum tunneling.