Young’s double-slit experiment provides strong evidence that light behaves as a wave through the observation of interference patterns, which are characteristic of wave behavior. Here’s how:
- Formation of Interference Fringes:
When light passes through two closely spaced slits, it creates a pattern of alternating bright and dark bands on a screen. This pattern arises from the superposition of light waves emanating from the two slits. - Constructive and Destructive Interference:
Bright fringes occur where waves from both slits arrive in phase and reinforce each other (constructive interference), while dark fringes occur where waves arrive out of phase and cancel each other (destructive interference). - Dependence on Wavelength:
The spacing of these fringes depends on the wavelength of light, which is a property of waves. This wavelength-dependent behavior aligns with predictions from wave theory. - Incompatibility with Particle Theory:
A particle theory of light, which treats light as tiny bullets, cannot explain the appearance of these regular patterns caused by overlapping waves. - Coherence Requirement:
The experiment uses coherent light sources (same frequency and fixed phase relation), necessary for sustained interference — a wave phenomenon.
Conclusion:
The clear, predictable interference pattern in Young’s experiment is a direct demonstration that light exhibits wave-like properties, confirming the wave theory of light.