# Homework Help: Thin-Film Interference

1. May 7, 2010

### aaronb

1. The problem statement, all variables and given/known data
A soap film with different thicknesses at different placers 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 (($$\lambda_{vacuum}$$=469nm)) from the reflected light, while anotyher loks magenta because destructive interference has removed green (($$\lambda_{vacuum}$$=555nm)). In these regions the film has the minimum thickness t required for the destructive interference to occur. Find the ration t$$_{magenta}$$/t$$_{yellow}$$

2. Relevant equations

$$\lambda_{film}$$ = $$\lambda_{vacuum}$$/ n

3. The attempt at a solution

i know from the problem that m =1 because it says minimum thickness. But after that I do not know how I should set up the problem using algebra or physics.