Constructive interference in light occurs when two or more light waves meet in phase — meaning their crests align with crests and troughs align with troughs. When this happens, the waves combine to form a wave with greater amplitude, resulting in a brighter or more intense light at that point.
Key points:
- Constructive interference occurs when the path difference between the waves is an integer multiple of the wavelength (like λ, 2λ, 3λ, etc.).
- It creates bright fringes in interference patterns.
- This phenomenon is a result of the superposition principle, where overlapping waves add their amplitudes.
- Constructive interference supports the idea that light behaves like a wave, not just a particle.
You can observe constructive interference in setups like the Young’s double-slit experiment, thin film interference, and holography, where bright patterns appear due to wave reinforcement.