Optics #3: The Dual Nature of Light; The Corpuscular Theory

Previously on optics #1, I explained explicitly how light is produced. Light is the very reason why you could see; hence the eyes is useless without light. This emphatically shows how important light is . You can now decipher the reason God created light before any other thing as believed by Christians and Jews

In the second series of optics I detailed lucidly the concept of light as a wave with enough convictions. You can have a read here

It is essential that you read through optics #1 and optics #2 for proper understanding of this optics #3

Introduction

Optics is the study of the properties, functions and application of light. Light can simultaneously behave as a wave and a particle

The wave theory deals with the behaviors of light as it interacts with matter. However, the wave theory could not explain sufficiently the whole characteristics of light as it interacts with space; properties such as Compton effect, photo-electric effect, light spectrum and other behaviors of light as it interacts with space failed to be explained by the wave theory. This brought alive what is ancestral to the wave theory of light_ the corpuscular theory of light

The Corpuscular Theory Of Light

The corpuscular theory of light emphasizes that light is made up of small discrete particles called corpuscles; otherwise, known as particles. So, this theory of light studies the behavior of light as it interacts with space. The corpuscular theory is similar to atomic theory; however, in atomic theory, atom is indivisible while in corpuscular theory,, atom is divisible(particles)
Interestingly, the particle theory of light(Corpuscular) is ancestral to the wave theory of light, the corpuscular theory of light was professed by Sir Issac Newton after series of experiments on light and it took some years before Hyugen pioneered the wave theory of light which later send the particle theory into extinction when the later failed to explain the wave boundary characteristics of light such as diffraction, refraction, refraction and interference. The particle theory of light was resurrected by Albert Einstein(the relativity theory pioneer) in the early 20th century

So, what did the wave theory of light fail to explain?

1. The Color Spectrum of Light

Newton's experiment of the color spectrum of light, was the first ever experiment that tended to describe light as a particle. Newton professed that the diffraction of light as proposed by Italian physicist Francesco Maria Grimaldi in 1665, was a type of refraction and that the structural nature of refraction and reflection could be only explained if light is assumed to be made up of particles(corpuscles); light travels in approximately straight line while waves do not. Newton bought his first prism in 1666_ref and experimented with it in a bid to prove his notion right.

When Newton joined the Royal Society of London in 1672_ref, he stated confidently that his whole experiments on light has proven that light is made up of particles and that diffraction of light is just a type of refraction as seen on his prism experiment_his prism experiment separated white light into different colors, this made him bring about the concept of color spectrum. Although spectrum has no division and its continuous, Newton choose to divide the spectrum into seven colors because seven was a mystical number according to an ancient Greek believe

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However, advocates of wave theory of light frustrated the veracity of Newtons's experiment; they stipulated that light waves is made up of white light and that the color spectrum seen through the prism is as a result of corruption within the glass. Newton proved those advocates wrong by experimenting with two prisms held at an angle . He passed a beam of white light through two prisms, the first prism split the light into spectrum while the second prism recomposed the spectrum into white light. Thus, Newton declared his experiment a crucial experiment because of his substantial evidence that the color spectrum was not caused by corruption in the glass prism. After the experiment, he ascertained that light is made up of different particles which combine to give a white light.

Howbeit, the advocates of the wave theory gave no attention to the particle theory of light, therefore declaring it unacceptable. Wave theory advocate like Robert Hooke also a member of Royal Society antagonized Newton's idea of "diffraction as a new type of reflection", he published that diffraction of light could only be articulated if light is assumed as a wave. This criticism from members of Royal city sent Newton's idea of "light as a particle" into extinction and mortalized the wave theory. Man really finds it difficult to forget what he believes and embrace a new idea or fact.
Although Newton persisted to convince other scientists to view light as particle when he became the president of Royal Society, his effort was futile.

2. The Photoelectric Effect

Photoelectric effect is the emission of electrons from some metals when light is incident on it. This electrons emitted is called photo-electrons. Albert Einstein who was an advocate of "light as a particle" proposed that light is not a wave; rather, a discrete packets of energy(photons) which are able to eject electrons out of a surface of some metals. He ascertained that light is made up of particles(photons) and that this photons collide with the atoms of metal when incident on the metal, thus, knocking out some electrons from the atoms of the metals if the energy of the incident light is greater than the work function of the metal. Einstein believed that light is made up of particles(photons) which can also be described as waves if it flows. So Einstein viewed light as a particle which is capable of producing a wave.
You can check my previous article on solar-electricity and solar panel for more understanding.

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The two theories of light pushed earlier scientist into confusion until Albert Einstein proposed the wave-particle duality of light. In his words, he said:

It seems as though we must use sometimes the one theory and sometimes the other, while at times we may use either. We are faced with a new kind of difficulty. We have two contradictory pictures of reality; separately neither of them fully explains the phenomena of light, but together they do. ref

His wave-particle dual theory of light brought the whole scientists into solace.

Conclusion

Light is a wave and also a particle. The two theories of light are needed for a proper understanding and application of optics. Employing one theory over the other to explain optics to students will project them into a total confusion

Did you miss any series on optics? Do well by taking a good read of any series missed:

References

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