Young's double-slit experiment is a fundamental experiment in physics that demonstrated the wave-like nature of light. It was performed by Thomas Young in the early 1800s and provided strong evidence for the wave theory of light.
In the experiment, Young shone a beam of light through a barrier with two narrow slits, creating two coherent light sources. The light passing through the slits then struck a screen, creating an interference pattern of alternating light and dark bands. This pattern was not expected if light was purely composed of particles.
The key observation in the experiment was the presence of interference fringes on the screen. Interference occurs when two or more waves interact, resulting in constructive or destructive interference depending on the phase relationship between the waves. The alternating light and dark fringes in Young's experiment indicated that light waves passing through the two slits were interfering with each other, producing areas of constructive interference (bright fringes) and areas of destructive interference (dark fringes).
This interference pattern arises due to the wave nature of light. When two coherent light waves meet, they can interfere constructively, reinforcing each other and creating bright fringes, or destructively, canceling each other out and creating dark fringes. This behavior is characteristic of waves.
The outcome of Young's double-slit experiment strongly suggested that light behaves as a wave, exhibiting interference phenomena. The experiment challenged the prevailing view of light as particles (corpuscular theory) and provided compelling evidence in favor of the wave theory of light. Later developments in quantum mechanics and the discovery of the photon as a particle-like entity with wave-particle duality further reconciled these seemingly contradictory behaviors of light.