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Please explain Quantum Tunneling
Science & Education
BY Guest
Monday 26th of June 2017


Quantum Tunneling - here is a simple real-life example which everyone was able to witness at least once in his/her life. Imagine a golf ball rolling inside a hole. In any point in time ball's energy is spread out between its kinetic energy and potential gravitational energy in proportion as to how high the ball is in relation to the hole's bottom. When ball reaches hole's highest point (like it is about to jump outside the hole) - there are two possible scenarios are about to rollout. If ball's cumulative energy surpasses potential gravitational energy as determined by ball's highest point - ball will jump out of the hole. If situation is reverse - ball will fall back towards the hole's bottom, to the opposite site of the hole's wall; in that moment ball's potential energy will equal to cumulative ball's energy - it will stop and roll back. In the second scenario - ball will never jump outside the hole, if additional kinetic energy is added to the ball - say by pushing it further. According to classical mechanics - ball will never leave the hole unless additional impulse is given to it (in order to fall outside the hole). In the quantum mechanics things are different. Potential barrier in quantum mechanics is "diffused" so to speak. It prevents particle's movement, but is NOT a impenetrable boundary as it is in Newton's classic mechanics. Particle itself in quantum mechanics is determined by a function which is connected with a possibility of finding a particle in a given place in a given time. If particle comes in contact with a potential barrier, Schrodinger's equation can calculate a probability of particle's penetrating through it. If potential barrier is rather low or cumulative energy of a particle is close to the highest - a wave function, although "dying away" as a particle is approaching a potential barrier - let's this particle overcome the barrier. So - particle will be "found" on the other side of a potential barrier - in "Newton's world" this would be impossible. This mechanism of a passing a particle through a potential barrier is called Quantum Tunneling. Thank you very much for your challenging question! Please visit us again and register to answer other kid's questions. Zacky

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