Light has been a mysterious topic for scientists. An age-old debate has been there between scientists to figure out the true nature of light. Light at its basic level can be understood as what is visible to us. The light which can be seen by human eyes is known as visible light. Some insects can see ultraviolet spectrum while dogs can only see shades of gray.
When we were kids, most of us were taught that light is a form of the ray. A phenomenon of refraction and reflection of light take place due to the ray like the behaviour of light. Light travels in a straight line and can bounce off surfaces following the law of reflection. This law states that the angle of incidence will always be equal to the angle of reflection.
But as we grew, a new concept was introduced to us that light behaves like waves. It undergoes interference and diffraction as any other wave would go. It also exhibits Doppler effect. But some phenomenon like Photoelectric Effect was not explained by the wave nature of light. The photoelectric effect is a process in which emission of electrons takes place from a metal surface when light with certain threshold frequency falls on it. After several experiments, it was found that light is made up of particles called photons. In our high schools, we read about the particle nature of light. So now this is confusing, and we do not know what exactly light is. To conclude we can say that light has dual nature: it behaves as a wave as well as a particle.
We can understand the wave-particle duality of light by an example. Take the political map of India, we find different states distinguishing them with the boundaries. In the physical map, we have rivers and mountains marked. Whereas in the roadmap, we have roads indicated on the map. Can we say that these all are not the maps of India? Of course, No. They all are maps of India only, serving different purposes. In a similar way, nobody exactly knows what light is. We just make predictions about it based on certain experiments and observations.
This article explains about the basics of light in a crisp way. To understand it in detail, watch the video.