Young’s double-slit experiment is a famous demonstration that light behaves as a wave. In this experiment, a beam of light passes through two closely spaced, narrow slits and falls on a screen behind them. Instead of forming just two bright spots, the screen displays a series of alternating bright and dark bands, known as an interference pattern.
This pattern occurs because the light waves coming from the two slits overlap and interfere with each other. Where the crests of both waves meet, they reinforce each other and create a bright fringe (constructive interference). Where a crest meets a trough, they cancel out, producing a dark fringe (destructive interference).
The experiment shows that light does not travel only in straight lines like particles but spreads out and interacts like waves. It provides strong evidence for the wave theory of light and helped confirm that interference is a fundamental property of wave motion.