A thin film of oil ( ) floats on water ( ) in air ( )
PHYSICS · Multi-part · Fermi University Physics · Optics & Photonics · Interference and diffraction · Interference and diffraction
Optics and Photonics, Ch Multiple-beam interference: thin films, multilayers and the Fabry-Perot etalon
Problem
A thin film of oil (n=1.45) floats on water (n=1.33) in air (n=1.00). It is viewed in reflection at θi=50∘ from the normal. For a component of vacuum wavelength λ=600 nm:
((a)) Use Snell's law to find the angle of refraction θt inside the oil.
((b)) Count the reflection phase at each surface (Chapter 6) and find the smallest non-zero oil thickness for which this wavelength is missing (dark) from the reflected light.