How does Light Work? Does it work as a wave or as a particle?

There have been countless scientific discussions about what light is and what it actually is over the centuries. According to some people, light behaves in a pattern similar to that of a wave in a pool, with small ripples in the pattern. According to a different viewpoint, light is nothing more than a particle, similar to the way that small droplets of water are generated when water is turned on from the kitchen faucet. At the same time that evidence for one viewpoint gained momentum, a counterargument appeared that led to confusion as well. Einstein called a tie in all of this when he stated that light has the properties of both a wave and a particle at the same time in the early twentieth century.

Light's Wave & Particle NatureSource: Pixabay

It was mostly those who followed Sir Isaac Newton who adhered to the light as a particle theory. In order to demonstrate the validity of his theory, he used a prism in order to show that light can be described as a series of particles. It is believed that Newton thought that light traveled in the form of a shower of particles, each of which followed straight lines until disturbed, due to the sharpness and clarity of the prism shadows.

Christian Huygens, a scientist who viewed light as a wave, as opposed to Newton's theory. Huygens suggested that diffraction and interference of waves provided proof that light was a wave. In addition to the wave-like properties of some materials, such as sound and water, there are also other types of wave-like behaviors that can cause diffraction, which occurs when waves bend around an object, as well as interference, which occurs when waves combine to produce greater or lesser amplitudes. Moving galaxies take on a different size as they move away from you and towards you, compared to waves from the source, which become longer as they move further away from you and shorter as they move closer to you. The Doppler Effect explains how sound intensity changes as the distance from the source progresses or as the source is moved closer to your location and away from you. Astronomers believed that light followed this effect. The visible light also seems to exhibit a similar characteristic in that the longer wavelengths appear to exhibit a redshift, whereas the shorter wavelengths are observed to exhibit a blueshift, such as the rainbow colors. It was not that long ago that scientists were convinced that light was a wave because of this overwhelming evidence. Albert Einstein settled this debate when he announced that light had dual properties, acting as a particle and a wave at the same time.

A phenomenon known as the photoelectric effect presents a significant obstacle for purists who believe that light exists as a wave. Photoelectric effect occurs when a metal surface is illuminated by light, causing electrons to be released into the air as they fly away from the metal. Although the higher intensity of light is having an effect on electron release, it is not causing more electrons to be released, as you might expect from a wave theory perspective. In fact, Albert Einstein, who is remembered for his seminal work on the subject, came up with a rather unique theory about the nature of light that demonstrates that it can be both a wave and a particle at the same time.

A wave of particles is created when light propagates toward a metal surface, and electrons are released as a result of interaction between an electron and one or more single photons rather than a wave as a whole, which is usually taken into account when measuring interaction with one single photon. A result of the transference of energy from that single photon is that the electron attached to that particular metal is knocked loose from it by the energy transference from the single photon. As a result of his work presenting the wave-particle duality in 1921, Albert Einstein received the Nobel Prize in Physics.

It has been acknowledged as such by physicists ever since Einstein first proposed this theory. As Einstein wrote, "we have two contradictory perspectives of the world; individually, neither opens up a complete explanation of light phenomena, however, when they are put together, they do." Understanding light as a wave led to the development of important technologies, such as lasers. The development of the electron microscope was made possible by the discovery of photons.

In the end, thanks to Albert Einstein's contribution, we can now declare that everyone is a winner since he has put an end to the decades-long debate.


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