This report serves to expose the results that emerged from the study of Young's double-slit experiment. One point the reader should pay attention to is the explanation of the interference effect. It is also interesting to note the importance of Young's work in relation to the development of the theory of light waves. Throughout history, philosophers and scientists have debated whether light acts like a particle or a wave. In the 17th century, the optical research of the Dutchman Christiaan Huygens suggested that light was wave-like. This movement is similar to the ripples seen above a body of water when an object is dropped into it. In the Treatise on Light (1690), Huygens' Principle explains that wave fronts are distributed such that the extent of the waves lies between the geometric parameters derived from its light source. Meanwhile in England, Isaac Newton was conducting his prism experiments to better understand light and color. Newton's corpuscular theory approaches the nature of light as a stream of particles. Due to Newton's influence, particle theory became widely accepted by the scientific community. Almost a century later, Thomas Young, an English doctor and physicist, became fascinated by the dilation of light after it passed through a thin slit. Then he began to discover the mysterious properties behind light. Although Newton's observations were sufficient for a macroscopic environment, they did not correctly anticipate results on a much smaller scale. Young challenged standard particle theory in the early 19th century. Young understood that sound traveled in waves. He recalled that when two sound waves interfere under the right conditions, they cancel each other out. The Englishman then hypothesized that this interference effect... in the center of the paper... like a wave, would behave like a wave. But when light was measured as a particle, the wave property of interference ceased. This has been coined the observer effect. A French scientist Louis-Victor de Broglie defined light as both a particle and a wave. Even with recent experiments, such as controlled Feynman double-slit electron diffraction, much remains to be learned about the characteristics of light. From research into Young's double-slit experiments, one can learn the intricacies of light. The interference effect, for example, indicates wave motion. Furthermore, the historical background of wave theory played a role in the formulation of Young's hypothesis. Likewise, the results of the experiment influenced the development of modern wave theory. In short, the double-slit experiment is proof that light can exhibit both corpuscular and wave qualities.