Wave–particle duality prostulates that all particles exhibit both particle and wave properties.
Light was thought either to consist of
-waves (Huygens) or of -particles (Newton)
The first to publicly hypothesize about the nature of light, proposing that light is a disturbance in the element air was Aristotle
However, Democritus, who was the original atomist – argued that all things in the universe, are composed of indivisible sub-components (Particles)
Through the work ofMax Planck, Albert Einstein, Niels Bohr,and many others, current scientific theory holds that all particles also have a wave nature (and vice versa).
This phenomenon has been verified not only for elementary particles, but also for compound particles like atoms and even molecules
So what is wave-particle duality?
The wave particle duality is the principle of quantum physics.
Holds that matter and light exhibit the behaviors of both waves and particles, depending upon the circumstances of the experiment.
It is a complex topic, but among the most intriguing in physics.
Wave-particle duality in light
Light is able to function as both a particle and a wave, depending on how the experiment is conducted and when observations are made.
Under certain conditions, such as when we shine it through narrow slits and look at the result, it behaves as only a wave can. Under other conditions, such as when we shine it on a metal and examine the spray of electrons that comes off, light behaves as only particles can.
This multiple personality of light is referred to as "wave-particle duality." Light behaves as a wave, or as particles, depending on what we do with it, and what we try to observe.
Wave-particle duality in matter
Just like light, matter is also capable of exhibiting properties of both wave-lengths and particles.
Massive objects exhibit very small wavelengths, so small in fact that it's rather pointless to think of them in a wave form.
However, in small objects, their wavelength is observable and in some cases significant.
Significance of this discovery
This discovery allows the behavior of light and matter to be able to be explained through the use of a differential equation which represents a wave function, which is at the heart of quantum mechanics.
We need the concept of alternating electromagnetic fields (waves) to explain certain physical phenomena, like the interference pattern in the 2 slit experiment. So we keep that. We must somehow explain how a particle orders of magnitude smaller than the distance between the slits somehow passes through both slits and interferes with itself. However we cannot explain this well using "quanta" (Particles, photons). Wave mechanics gives a simple easy to understand explanation.
Significance of this discovery
We need the concept of quanta (particles, photons) to explain other phenomena, like the Photoelectric Effect. So we keep that too. But, this means we use 2 different, mutually exclusive systems of mechanics to explain electromagnetic radiation.
The attempt to explain what the wave particle duality "actually means" is a key point of debate in quantum physics. Many interpretations exist to try to explain this, but they are all bound by the same set of wave equations and not breakthrough yet has occurred.