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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!

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Solution Summary

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