Sunday, March 2, 2014

Wave-Particle Duality of Light

On the wave-particle duality of light.
or
It’s a matter of time, space, and relativity.




Understanding light is the key to understanding the universe. Not just because emitted or reflected electromagnetic radiation –light – allows us to see the cosmos, but because the rules found to govern the genesis and behavior of light may lead to deciphering the actual nature of all subatomic particles and the structure of the universe.

The Paradigm

Figure 1 Absorption and emission of photons.











Photons of light are produced when an atom’s electrons drop from higher to lower energy states. Introductory physics teaches that the photons of light behave both as waves and particles.  Its wave like nature can be demonstrated by the interference pattern produced during a double slit experiment. Its particle nature, the photon, can best be shown by photoelectric effect. Its dual nature, by the way light reflects and refracts. Quantum physics theorizes the wave-particle duality for all matter, but is most noticeable in small, subatomic, particles.

A paradox arose when investigating lights duality. In a double slit experiment set up with one photon being produced at a time, an interference pattern was still seen; it was as if the photon was interfering with itself. But if a particle detector was placed in one of the slits the interference pattern disappeared – the photons ceased to act as waves and behaved as particles. 

Beyond the Paradigm

How light can behave both as a wave and a particle is easier to explain if you approach the problem from the photon of light’s perspective. An important principle of relativity states that as speeds increase, time slows. At the speed of light, time ceases to have meaning; it stops. Therefore light itself does not experience time. Everything that happens to a photon in our universe, from the time it is generated till it is absorbed - as far as the photon is concerned - happens simultaneously. Distances are meaningless to light. If distance equals rate times time and time goes to zero, all distances go to 0. For light there is no difference between traveling to an abutting atom or clear across the universe. The distance is the same; there is none. When a photon is produced, it fills the space it exists in. From the light’s perspective, it instantaneously fills its universe. But in the universe as we perceive it, the photon would be described as a wave of energy moving away from its source at the speed of light (C). And if unabsorbed, the light would continue to spread out to fill the universe. But if at any point in our perceived universe the photon is absorbed, the apparent wave disappears. Thus light is a particle and appears as a wave. In the double slit experiment, the photon does interfere with itself because the photon is entering both slits at the same time. If the photon is absorbed, it disappears everywhere at the same instant.

Questions that need answers:

How does an electron dropping energy levels actually produce a photon?

How does an electron absorb a photon?

When electrons drop energy levels they release energy in the form of photons.  The more levels dropped the more energetic the photon and the greater the time difference between levels. What happens to time as electrons are transitioning between energy levels?

Are the discreet energy levels of atoms related to the time differential between levels?

What effect does speed of a charged particle have on the particle’s charge?

If the faster a charged object is moving the slower its time flows (even if the difference is minuscule), what effect does the difference in time flow have on the particle’s charge?

If energy equals mass times the speed of light squared, and at the speed of light time stops; how important is time to the structure of what we call mass or matter?

What is the role of time, if there is one, in the wave-particle duality of all matter?

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