What is Young's Double-Slit Experiment?
Young's Double-Slit Experiment is a classic physics experiment demonstrating the wave-like nature of light and, later, the wave-particle duality of matter. It involves shining a light source through two closely spaced slits, observing the pattern formed on a screen behind them.
How the Experiment Works
When light passes through the two slits, it behaves like a wave. Each slit acts as a new source of waves, which then interfere with each other. Where wave crests meet, they reinforce (constructive interference), creating bright bands. Where a crest meets a trough, they cancel (destructive interference), creating dark bands. This produces a characteristic interference pattern of alternating bright and dark fringes on the screen.
Demonstrating Wave-Particle Duality
Remarkably, even when single photons (particles of light) are sent through the slits one by one, they still build up an interference pattern over time. This suggests that each individual photon somehow passes through both slits simultaneously, interfering with itself, highlighting the perplexing wave-particle duality. The act of observation (e.g., trying to detect which slit the photon passed through) collapses its wave function, causing it to behave purely as a particle and eliminating the interference pattern.
Importance and Applications
This experiment is fundamental to quantum mechanics, illustrating that particles do not just have a definite position and momentum, but exist as probability waves until measured. Its principles are crucial for understanding quantum phenomena, quantum computing, and the behavior of subatomic particles, influencing technologies like electron microscopes and quantum encryption.