Ultimate Enigma
Wave-particle duality
Particles also behave as waves and vice versa.
The enigmatic aspect of the elementary particles is that they behave both as particle and wave. Since Newtonian mechanics cannot explain it, the need for quantum mechanics arises. As for example, low frequency electromagnetic radiation tends to act more like a wave than a particle whereas high frequency electromagnetic radiation demonstrates wave nature. That light has the characteristics of both wave and particle has been a subject of debate since the time of Newton until Einstein. By 1930's, through the works of physicists Max Plank, Louis de Broglie, Niels Bohr, Werner Heisenberg, Max Born and others, it was thoroughly established that all particles from molecules, atoms to sub-nuclear particles demonstrate wave-particle duality. In 1909, a scientist named Geoffrey Taylor, conducted an experiment in which he observed light coming out of a couple of small holes. He photographed the light (projected from a movie) coming out the holes with a special movie that was sensitive to light. When the light was turned down to a very dim level, Taylor's photographs showed tiny pinpoints of light scattering out of the holes which showed light was actually a particle. On the other hand, when the same dim light was allowed to shine through the hole for a long period of time, the dots (particles) eventually filled up to make an interference pattern which was wave-like. Later, it was Louis de Broglie who suggested that matter also might act that way. Afterwards, scientists performed the same kind of experiments with electrons and discovered that electrons, like photons (light particles), are also particle and wave at the same time.
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