Particle, Waves, and Duality
In a basic physics course, one is introduced to the concept of particles and waves. The understanding evolves with the intuitive concepts of particles colliding with each other to exchange energy and momentum; and waves interacting with each other to create interference patterns. Such everyday observations may be explained by using Classical mechanics, also known as Newtonian mechanics. However, at the atomic scale, this simple everyday intuitive picture does not hold. Whether an electron behaves as a particle or a wave depends on the circumstances. Sometimes, it may collide with other electrons and barriers just like a particle. At times, it behaves like waves and in fact, creates interference patterns! It may also transmit through barriers, a phenomenon called quantum mechanical tunneling, which has no classical analog.