Light has been studied by scientists throughout the years. Two models were the results of those years of research, the first model is called particle theory that was presented by Isaac Newton in the 17^th century, Newton thought that light is composed of particles because this would account for the straight rays and sharp shadows. Later, Thomas young presented the wave model that was a broader theory than the particle theory.

Newton explained that every color would have a different angle of refraction. He observed that all objects appear to have the same color when the beam of colored light illuminates them, and that beam remains the same in terms of its colors no matter how many times it’s refracted or reflected. The conclusion is that color is a property of the light that reflects from objects not a property of the objects themselves [1].

Newton’s theory failed to explain two difficulties, first one is that light goes from one medium to another, some of it is refracted and some of it is reflected. Secondly, Newton couldn’t explain the interference and diffraction. To face these difficulties Newton presented a periodic activity connected with moving particles. He considered sharp shadows to be hard to understand with waves [1].

Thomas Young provided strong evidence for Huygens’ wave theory of light in 1803, when he presented the results of his double-slit experiments. Young stated that light is composed of particles, then all of these particles should pass through a single slit, as a result, they create bright patterns on the other side of the slit. Also, if light is composed of waves, then the slits will cause diffraction, and the light should result in a predictable interference pattern, in the same way that water waves do [2].

Young showed in his experiments that light behaves like a wave and creates an interference pattern, which is the superposition principle[2]. Once he found out that light is made of waves he estimated the wavelengths of individual colors using data from Newton. Therefore, one can look at the two theories as a combination of each other, where the wave theory studies light in a broader way.

References:

Newton, I., Philosophical Transactions of the Royal Society 1672, 80, 3075–3087.