Review Conceptual Example 4 before beginning this problem. A soap film with different thicknesses at different places has an unknown refractive index n and air on both sides. In reflected light it looks
multicolored. One region looks yellow because destructive interference has removed blue (λvacuum = 469 nm) from the reflected light, while another looks magenta because destructive interference has removed green (λvacuum = 555 nm). In these regions the film has the minimum nonzero thickness t required for the destructive interference to occur. Find the ratio tmagenta/tyellow.