spite of this, for over one hundred years, Newton’s particle model was firmly believed and preferred over the wave model. This was partly because of its simplicity and partly because of Newton’s influence on contemporary physics. Then in , Young performed his double-slit experiment and observed interference fringes. This phenomenon could be explained only by wave theory.
It was realized that diffraction was also another phenomenon which could be explained only by wave theory. In fact, it was a natural consequence of Huygens idea of secondary wavelets emanating from every point in the path of light. These experiments could not be explained by assuming that light consists of particles. Another phenomenon of polarisation was discovered around , and this too could be naturally explained by the wave theory.
Thus wave theory of Huygens came to the forefront and Newton’s particle theory went into the background. This situation again continued for almost a century. Better experiments were performed in the nineteenth century to determine the speed of light. With more accurate experiments, a value of × m/s for speed of light in vacuum was arrived at.
Around , Maxwell proposed his equations of electromagnetism and it was realized that all electromagnetic phenomena known at that time could be explained by Maxwell’s four equations. Soon Maxwell showed that electric and magnetic fields could propagate through empty space (vacuum) in the form of electromagnetic waves. He calculated the speed of these waves and arrived at a theoretical value of . × m/s.
The close agreement of this value with the experimental value suggested that light consists of electromagnetic waves. In Hertz demonstrated the generation and detection of such waves. This established the wave theory of light on a firm footing. We might say that while eighteenth century belonged to the particle model, the nineteenth century belonged to the wave model of light.
Vast amounts of experiments were done during the period - on heat and related phenomena, an altogether different area of physics. Theories and models like kinetic theory and thermodynamics were developed which quite successfully explained the various phenomena, except