The difference between constructive and destructive interference in diffraction lies in how the overlapping light waves combine:
- Constructive Interference:
- Occurs when the waves meet in phase — their crests align with crests and troughs align with troughs.
- The amplitudes add up, producing a brighter or more intense light region called a bright fringe or maximum.
- Happens at points where the path difference between waves is an integer multiple of the wavelength (0, 1λ, 2λ, etc.).
- Destructive Interference:
- Happens when the waves meet out of phase — the crest of one wave aligns with the trough of another.
- The waves cancel each other out, producing a dark or less intense region called a dark fringe or minimum.
- Occurs where the path difference is an odd multiple of half wavelengths (½λ, 1½λ, 2½λ, etc.).
In diffraction patterns, the alternating bright and dark fringes result from these two types of interference between the diffracted waves.