1. The problem statement, all variables and given/known data (a) Calculate the minimum thickness of a soap bubble film that results in constructive interference in the reflected light if the film is illuminated with light whose wavelength in free space is λ=600nm. The index of refraction of the soap film is 1.33. (b) What is the film is twice as thick? Does this situation produce constructive interference? 2. Relevant equations Constructive interference occurs here, so: 2nt = (m + ½)λn 3. The attempt at a solution (a) Part A is pretty straightforward, as it just involves recognizing that this is a constructive interference case and then plugging in what we know. 2nt = (m + ½)λn t = (0 +½)λ / 2n = λ / 4n = 600nm / 4(1.33) = 113nm (b) The answer for Part B shows: t = (m+½)λ/2n = (2m + 1) λ/4n m = 0, 1, 2... "The allowed values of m show that constructive interference occurs for odd multiples of the thickness corresponding to m=0, t=113nm. Therefore, constructive interference doesn't occur for a film that is twice as thickness I'm confused as to what exactly they did to arrive at this conclusion. What is meant by "odd multiples of the thickness"? The answers doubled every value in the above equation except for thickness (t). Why wouldn't this be done, as the question is specifically asking "what if the film was twice as thick"?