A soap film with an index of refraction n = 1.33 is contained within a rectangular wire frame. The frame is held vertically so that the film drains downwards and approximates the shape of a wedge with flat faces near the top. The thickness of the film at the very top is essentially zero. The film is viewed in reflected white light with near-normal incidence, and the first violet (λ = 420 nm) interference band is observed 3.00 cm from the top edge of the film.
[Figure: Vertical soap film in rectangular frame showing wedge shape]
1) Locate the first red (λ = 680 nm) interference band.
2) Determine the film thickness at the positions of the first violet and the first red interference bands.