Final answer:
The double slit experiment illustrates that light has both wave-like and particle-like properties, demonstrating the principle of wave-particle duality. It provided definitive proof of the wave character of light through the formation of interference patterns, but other experiments show light’s particle nature, depending on the setup.
Step-by-step explanation:
The double slit experiment demonstrates that light cannot be explained solely as a wave or just a particle; instead, it exhibits characteristics of both, known as wave-particle duality. Young's double slit experiment showed an interference pattern, which is indicative of wave-like behavior. Yet, phenomena like the photoelectric effect indicate light also has particle characteristics, leading to the conclusion that light exhibits both behaviors.
Einstein's findings added to this mystery, showing that depending on the experimental setup, light could exhibit wave-like or particle-like properties, but not both simultaneously. The double slit experiment is pivotal in the study of quantum mechanics and has led to significant advancements in our understanding of the fundamental nature of light and matter.