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Wave Optics: Interference through thin films.

1.) A mixture of yellow light (wavelength = 582 nm in vacuum) and violet light (wavelength = 414 nm in vacuum) falls perpendicularly on a film of gasoline that is floating on a puddle of water. For both wavelengths, the refractive index of gasoline is n = 1.40 and that of water is n = 1.33. What is the minimum nonzero thickness of the film in a spot that looks the following colors because of destructive interference?
a.) yellow
b.) Blue

2.) Light of wavelength 626 nm (in vacuum) is incident perpendicularly on a soap film (assume n = 1.36) suspended in the air. What are the two smallest nonzero film thicknesses (in nm) for which the reflected light undergoes constructive interference?
a.) Smallest
b.) Next smallest

I don't really understand this section and am therefore having some difficulty with these problems. I can't seem to put an equation to these problems. Any help would be greatly appreciated and thank you!

Solution Summary

Tow problems related to interference through thin films are discussed and solved.