Human beings have been trying to understand how light works since the time of the Ancient Greeks. In roughly 300 BC Euclid studied the properties of light, he thought light travelled in straight lines and described the laws of reflection. In 1690 Sir Isaac Newton came out with the corpuscular theory of light, he believed that light was shot out of a source in small particles. Also, in the 17th century the Dutch astronomer Huygens suggested a wave theory of light he thought that light was a longitudinal wave. He said that this wave travelled through a material called the aether. As light can pass through vacuum and travels rather fast, he has some strange thoughts about the properties of the aether, for example – it must fill all space and be weightless and invisible and for that reason for many years other scientists doubted his theory. The quantum theory proposed by Max Planck in 1900 which was later developed by Einstein, put the wave and particle theory together and he showed that light can sometimes act like a particle and act like a wave. Prior to his quantum theory Max Planck also worked on light in the late 19th century and he came up with a constant and he called that Planck’s Constant in which he used the letter V for light and soon after Einstein used that constant to help him conduct some of his research for his theories of relativity that helped him work towards his Nobel Peace Prize in Physics.
Sir Isaac Newton
Newton was credited with one of the three most important discoveries in relation to understanding light when he carried out ‘optical research into the spectral decomposition of light’. In 1700 Newton produced a theory in which he concluded that light was a group of particles, he thought this because when he split the sunlight up into the colors of the spectrum, the shadows gave evidence that the light had traveled in particles and not a wave therefore he concluded that light was a group of particles travelling in the air.
He developed what he called a pulse theory which compared the spreading of light to those of waves in water to explain the origins of colors in 1672 he theorized that light’s vibrations could be perpendicular to the direction of propagation.
The second person who gave a contrasting opinion to Newton was Christiaan Huygens. Huygens said that light travelled in waves after he carried out an experiment that proved that light bent going through a denser medium such as glass, therefore he then theorized that light came in waves because it appeared to bend or refract through that denser medium and then he thought that if it was particles going through a denser medium then they would do the opposite and actually speed up rather than bend and slow down.
The third person who had a theory on how whether light was a particle or wave was Thomas Young. He theorized that in 1807 light acts like a wave because when he carried what he called the double slit experiment he thought that light acted like a wave because he shone a light at a surface with two slits in it and placed a screen on the other side when the light went through the slits it would show as a stronger beam of light on the screen but it would also show the light moving outward and shining on the screen in a sort of wave thing. He also proposed that different colors were created by different lengths light waves.
The fourth scientist that took part in the theory of light was James Maxwell who discovered that self-propagating (self-sustaining) electromagnetic waves will travel through space at a constant speed which was equal to the previously measured speed of light which he concluded that light was a form of electromagnetic radiation. Maxwell’s theory was confirmed by Heinrich Hertz by generating and detecting radio waves in the laboratory and proving that these waves behaved exactly like visible light showing properties such as: reflection, refraction, diffraction and interference.
He is the final scientist that worked on the theory of light, he is known as one of the best scientific minds ever his name was Albert Einstein. Einstein discovered that light was neither only a particle or a wave but was in fact a ‘photon’ (a particle representing a quantum of light or other electromagnetic radiation. A photon carries energy proportional to the radiation frequency but has zero rest mass). He published three papers in the early 20th century. In those papers he came to the conclusion very similar to Max Planck that light was both a particle and a wave. However, he concluded with a theory he called the theory of special relativity. In his theory of special relativity in 1905 he theorized that the laws of physics are the same for all non-accelerating observers and that the speed of light in a vacuum was independent of the motion of all observers.
In conclusion, it took all of these scientists and many more, all the way from the time of the Ancient Greeks to the present day to develop the ideas and the knowledge through observation and experimentation each developing their own theories and conclusions some very different from others but all equally useful which has concluded with Einstein and his theory of relativity in which he found that light acts as both a wave as theorized by Huygens and also a particle as theorized by Sir Isaac Newton which he then called a photon from all of the works that these scientists have carried out we now believe to have quite a good understanding of light and the colors of the visible light spectrum which has since furthered our knowledge of the non-visible light spectrum such as infrared, and the electromagnetic spectrum.