Term Paper on Wave Particle Duality | Quantum Theories | Physics

Here is a term paper on wave particle duality.

Throughout history, science has been fascinated with light and how it behaves. Prisms, among other tools, have been used to observe and measure light. During the 1600s, Christiaan Huygens and Isaac Newton suggested opposite theories to explain the behavior of light. Huygens believed that light functioned as a wave, with various lengths.

On the other hand, Newton proposed that light didn’t behave as a wave, but as a particle. Newton’s position in the scientific community of the time helped make his theory dominant, while Huygens dealt with issues of matching observation to his theory.

To understand how these theories differ, one has to understand how waves and particles behave. We’ll use light as an example. Across the electromagnetic spectrum, light waves behave in very comparable ways. When a light wave comes across an object, it is either polarized, transmitted, absorbed, refracted, diffracted, reflected, or scattered.

What happens to the light wave depends on its wavelength and the structure of the object encountered. Scientists also structure various experiments that allow them to study light by forcing it into different situations where the light is made to bounce off specific objects or bend. The data gathered becomes part of the knowledge database that others use to build their experiments and theories. So how does a wave occur?

Generally, a wave has to propagate through some type of medium. Huygens defined that medium as luminiferous aether, but today it is known simply as ether. This explanation was accepted in the scientific community, even though there was no concrete proof it existed. During the 1860s, James Clerk Maxwell quantified a set of equations (known as Maxwell’s laws or equations) to describe electromagnetic radiation along with visible light as the transmission of waves.

He assumed such an ether was the medium of propagation. His predictions with this medium in mind were consistent with his experimental results. However, no such ether was ever located, but instead it remained a mystery.

Yet the scientific community could not provide an alternative that would explain the experimental results being observed without it. But as we shall see throughout these article, scientists continued to make breakthroughs and thus were able to craft theories that appeared to fit the phenomenon that they were observing. In addition, experiments have also built a record that current scientists are using to move this field of study ever forward.

In 1720, James Bradley completed astronomical observations in stellar aberration. He found that ether, if it existed, would have to be stationary relative the movements of Earth. Throughout the 1800s, many experiments were created to detect the ether or its movements directly, but with no success.

The most famous experiment of that era was the Michelson-Morley experiment, an attempt to measure the movement of the Earth through ether. Though often called the Michelson- Morley experiment, it refers to a series of experiments first carried out by Albert Michelson in 1881.

Then those experiments were carried out again with superior instruments and equipment at Case Western University in 1887, with assistance from Edward Morley, a chemist.

Light was known to travel through outer space. Scientists believed that space was a vacuum. One could create a vacuum chamber and shine a light through it. The evidence was clear that light could move through regions without air or other matter. So how could that be? Huygens’ ether was the handy substance scientists used to explain how this was possible.

The universe, they claimed, was filled with ether. It was this substance that gave light waves the ability to travel through space and other regions commonly lacking air or any other matter.

Michelson and Morley decided that if the ether did exist, you should be able to measure Earth’s orbital rotation through it. Since ether was believed to be unmoving (static except for the vibration) while the Earth was moving quickly, it stood to reason that one could measure ether by its contact with the Earth. Therefore, researchers and scientists began to build experiments meant to capture measurements of ether in these interactions with the Earth.

Imagine for a moment holding your hand outside your window, particularly in a car. While it may not be windy, the force of your own motion (courteous of the car) makes it appear windy. Scientists believed ether should have created what would be in effect an ether wind, which would push or hinder the motion of a light wave.

To test this hypothesis, Michelson and Morley designed a scientific device, called the Michelson interferometer, which was meant to split a beam of light, then bounce it off mirrors so that the split beam moved in different directions then struck the target.

The principle at work was based on the idea that if two beams traveled an equal distance, but used different paths to move through the ether, they should end up moving at different speeds. So when these beams finally hit the target screen, they would be slightly out of phase with each other, creating an observable interference pattern that could be measured. If this experiment had been successful, it would have been the first definitive proof of the existence of this ether.

The results was disappointing, however, because they found absolutely no evidence of the relative motion bias that these two scientists were hoping to observe and measure. No matter which path the split beam of light took, the light always seemed to be moving at precisely the same speed, so there was no interference to measure. Without evidence of interference, scientists found it difficult to move forward with this particular line of study. After all, with no evidence of the ether in the expected places, scientists began to think that this might not be a productive line of study.

Ether was finally abandoned with the work of Albert Einstein and his theory of wave particle duality. In 1905, Einstein published his paper explaining the photoelectric effect, in which he proposed that light travel in discrete bundles of energy (quantum). The energy contained with a photon was related the frequency of light. As a result, ether was no longer the necessary medium it had once been. But how did this explain the situations when light was observed acting as a wave, and other times when light acted as a particle?

Experiments, such as the quantum variations of the double slit experiment and the Compton Effect, seemed to confirm that light was in fact a particle. But as experiments continued and the evidence mounted, it became clear that light could act as a wave or a particle depending on the parameters of the experiment and when the observations were made.

Researchers and scientists pondered how such an effect could occur. After all, they understood that matter could exist in different states, but never two or more at the same time. Yet, particles of light were doing just that. This moved the research forward, because there had to be an explanation for this occurrence. Now let’s discuss how the wave particle duality translated into from light to matter.

Wave Particle Duality in Matter:

Scientists wondered if matter would also show such duality. The de Broglie hypothesis was an extension of Einstein’s explanations of matter’s wavelength in relation to its momentum. For de Broglie, Einstein’s relationship of wavelength to momentum seemed able to determine the wavelength of any matter.

His reasoning for choosing momentum over energy is based on the various energy types available to use in the equation, such as total, kinetic or total relativistic energy. For photons, it wouldn’t matter because all energy is the same in that instance. But matter is different and so momentum was this 1929 Noble Prize winner’s choice.

Just like light, it seemed that matter also exhibited both wave and particle properties under precise circumstances. Obviously, massive objects would exhibit very small wavelengths. But for small objects, it is possible to observe the wavelength, as noted in the double slit experiment with electrons.

So now the same behavior was being observed in several different settings. Researchers and scientists recorded the data, and then began to study it to determine why these effects were occurring, attempting to come up with a theory and equation to fit the observations.

But what does it matter if light or matter acts as a wave and a particle?

Significance of Wave Particle Duality:

The major significance of this theory is that all behavior of light and matter can now be explained through an equation that denotes wave function, generally found in the form of the Schrodinger equation. As a result, describing reality in the form of waves is the heart of quantum mechanics, the mathematical brain of quantum physics.

The most common interpretation of this theory is that the wave function simply represents the probability of locating a given particle at a given point. These probability equations can exhibit supplementary wave-like properties, creating a concluding probabilistic wave function exhibiting these properties also.

In other words, the probability of a particle being present in any location is a wave, but the actual physical appearance of that particle isn’t a wave at all. Instead, it is a particle but not until the moment that it is measured in that particular place or space.

The complicated math can result in fairly accurate predictions, the physical meaning of these equations are much harder to grasp. Explaining what the wave particle duality really means continues to be a key point of debate. These debates have created multiple interpretations to explain this particular duality, but at the same time these interpretations are bound by unambiguous wave equations, and are required to explain the same experimental observations. No easy task, as science continues to dig into what this theory means to the real world.

As studies continued in the realm of quantum physics or mechanics, evidence of other types of behavior by electrons and atoms began to mount. Scientists worked to discover what the cause of these effects was. As a result, the many areas of study in quantum physics began to develop.