Nature of Light

The question whether light is a wave or a particle has a very interesting and long history. Early theories considered light to be a stream of particle which emanated from a source and caused the sensation of vision upon entering the eye. The most influential proponent of this particle theory of light was Newton. Using it, he was able to explain the law of reflection and refraction. The chief proponents of the wave theory of light propagation were Christian Hygens and Robert Hooke. Hygen's using his wave theory was able to explain reflection and refraction. Newton was the virtues of the wave theory of light particularly as it explained the colour formed by thin films,  which Newton studied extensively. However, he rejected the wave theory because of the observed straight line propagation of light. Because of Newton's great reputation and authority, this reluctant rejection of the wave theory of light, best an lock of evidence of diffraction was strictly adhered to by Newton's followers. Newton's particle theory of light was accepted for more than a century.

    In 1801 Thomas Young receive the wave theory of light. He was one of the first to introduce the idea of interference as a wave phenomena in both light and sound. His observation of interference with light was a clear demonstration of the wave nature of light. Young's work went unnoticed by the the scientific community for more then a decade.

     Fresnel performed extensive experiments on interference and diffraction and the wave theory on a mathematical basis. He showed, that the rectilinear propagation of life is a result of very short wavelength of visible light. In 1850 Jean Foucault measured the speed of light in water and showed that it is less than that in air, thus ruling out Newton's particle theory according to whom the speed of light is more in water.
    But the drama was not yet over. The climax came when the wave theory of light failed to explain the photoelectric effect invented by Albert Einstein in 1905. He himself explained it on the basis of particle nature of light.  An amicable understanding was ultimately reached in accepting that light has dual nature. It can behave as particle as well as wave depending on its interaction with the surrounding. Later it was found that even the well established particles such as electrons also have a dual character and can she interference and diffraction under suitable condition.