1. The problem statement, all variables and given/known data A very thin oil film(n=1.25) floats on water(n=1.33). What is the thinnest film that produces a strong reflection for visible light with a wavelength of 700nm? 2. Relevant equations [tex]\lambda[/tex]=(2nd)/(m-0.5) d=(m-0.5)*([tex]\lambda[/tex]/2n) thinnest film has m=1 3. The attempt at a solution d=(0.5*700)/(2*1.25)=140nm This answer is incorrect. Is there a problem in my technique?