Is light a wave or a particle?

Sir Isaac Newton gave a theory of light- called the corpuscular theory of light. As soon as the light particles reach some material mediums like glass, water, etc., the particles are attracted by a force (F = ma) and the particles will be accelerated in the medium, resulting into an increase of speed. This means that light should travel faster in material medium than in a vacuum. But this theory failed when Olaf Roemer, Armand Fizeau, Leon Foucault and other experimentalists measured the speed of light, the result of which showed that the speed of light in a material medium be less than that in a vacuum. To comply with the experimental observations, the wave theory of light was proposed at about the end of the 18th century by Christiaan Huygens. A deeply-rooted concept is difficult to change at once. The world had to wait about a hundred years to accept that light was a wave until when Thomas Young first demonstrated the interference of light in his famous double-slit experiment in 1801. 'Light is a wave' was now established. It remained like that until the end of the 19th century. One of the three groundbreaking papers of Albert Einstein in 1905 was on the photoelectric effect. The phenomenon of photoelectric effect couldn't be explained if light behaved like a wave. Therefore, he proposed the particle theory of light. Light consisted of 'quanta' (packets) of energy-which he called 'photons.' His theory explained the phenomenon of the photoelectric effect without any discrepancy, proving that light shows a particle-like nature. Although the fame of Einstein spread all over the world by his work on the Theory of Relativity, he was awarded the Nobel Prize of Physics in 1921 for his discovery of the law of the photoelectric effect.
Thus, light shows a dual nature - wave like nature in the phenomena of reflection, refraction, diffraction, interfernece and polarization but particle-like nature in the phenomenon of the photoelectric effect.