AP Physics 2 / Unit 14: Waves, Sound, and Physical Optics
14.9 Thin-Film Interference
Notes
Light reflecting from the top and bottom of a thin film interferes, causing colors (soap bubbles, oil slicks).
- Reflection off a higher-$n$ medium adds a half-wavelength phase shift.
Practice
Soap bubble colors come from:
Reflections interfere.
Light reflecting from a medium with higher $n$:
Like a fixed end.
Changing the film thickness changes:
Path difference changes.
Ready for more? Take the Unit 14 test.