Thin-film interference occurs when light reflects off the upper and lower boundaries of a thin layer—like soap bubbles, oil slicks, or anti-reflective coatings—and the reflected waves interfere with each other.
How it works:
- Light partially reflects off the top surface of the film and partially transmits through and reflects off the bottom surface.
- The two reflected waves interfere, either constructively or destructively, depending on their path difference and phase shifts.
- This interference varies with film thickness, wavelength of light, and viewing angle.
Result:
The interference leads to vivid colors seen in thin films, as different wavelengths (colors) are enhanced or suppressed. That’s why soap bubbles shimmer and oil slicks display rainbow patterns.
Applications:
Used in optical coatings, anti-reflective lenses, and measurement techniques in nanotechnology.