Light. What is it? How does it enable us to see? And how does it behave? Since time immemorial, humans have pondered about it. Newton had proposed that light is made of tiny particles called "corpuscles." This theory insisted that sources of light gave out perfectly elastic, rigid, and weightless particles that travel in a straight line with finite velocity and some kinetic energy. However, this sparked a debate for this theory could not explain phenomena of partial reflection and partial refraction. This theory also failed to show the phenomena of polarization, diffraction and interference.
To counter this another scientist, Christiaan Huygens, proposed that light is not made of particles but instead acts as waves. This eliminated the demerits of Newton's corpuscular theory but presented demerits of its own. This theory failed to explain the rectilinear propagation of light (phenomenon of light travelling in straight lines), the photoelectric effect (phenomenon of electrons being emitted when struck by photons) among others.
Throughout many years this debate continued until Thomas Young, the scientist who is primarily known for the Young's Modulus (used to measure elasticity of materials), performed his famous double slit experiment. This solidified the wave nature of light.
However in the annus mirabilis, Einstein theorised the famous photoelectric effect. He proposed that light, in the form of particles, on striking matter can liberate electrons. This theory was later proved by Robert Millikan. However, the dilemma still persisted. How could light under some conditions act as a wave and under other conditions as a particle?
This problem was solved in around 1925 by the scientist de Broglie who solved that not only light but even matter carrying particles can behave as a wave.
Below is a simple recreation of the double slit experiment done by myself
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