A-Z Blogging Challenge: Wave-Particle Duality

Example of a double slit experiment, by Timm Weitkamp,
CC-BY-3.0-de. SOURCE.

Wave-particle duality is a principle of quantum physics that says matter and light act as both waves and particles, and that the observed behavior depends on the experiment.

Since the 1600s, scientists tried to figure out whether light, a type of electromagnetic radiation, came in waves or was made up of particles. Christiaan Huygens developed a wave theory (also suggesting that there was a luminiferous ether through which waves traveled, since it was generally thought waves needed a medium) and Isaac Newton a particle (or corpuscular) theory. It wasn't until the 1800s with Thomas Young's double-slit experiment and the buildup of other evidence pointing toward the fact light acted like a wave that Newton's theory was overturned. At least until the Michelson-Morley Experiment, which tried and failed to find any ether.

There are six major types of light phenomenon: reflection, refraction, interference, diffraction, polarization, and the photoelectric effect, all of which can be explained by wave theory, except for the photoelectric effect. Then Albert Einstein published a paper that explained it (introducing photons as continuous waves in 1905), wave-particle duality was also proved to take place with matter by Louis de Broglie (who was awarded the Novel Prize in 1929), and Niels Bohr proposed that light could take on either wave or particle characteristics. Hence, with no other explanation, duality was accepted as reality.

Example of an interference pattern, by Thierry Dugnolle,
public domain image. SOURCE.

One of the more famous experiments done which helped prove wave-particle duality was Young's Double Slit Experiment. To take Richard Feynman's analogy, imagine someone shooting at a wall through two slits in a sheet of metal. You would expect the bullets to be centered close to two narrow bands on the far wall--but with light, that isn't true. Instead (to stretch the example a bit far) the pattern of bullets would show up as an interference pattern (bright and dark bands, in the case of light; see above image) as though projectiles were passing through the slits at the same time and bouncing off each other.

No notable scientist today. Quantum physics is far from stagnant, of course, but I don't know of any wave-particle dualicists. But if you'd like a simulated ripple tank to play around with that has an example of the double-slit experiment (just make sure you have Java):

http://www.falstad.com/ripple/ex-2slit.html

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