Reflective coatings are designed to increase the reflectivity of surfaces for optical applications. The figure below shows a reflective coating composed of two layers having refractive indices n' = 3/2 and n = 6/5. To be effective, all three reflected rays shown must be in phase. In the following questions you are to assume normal incidence. (be careful with phase shifts!)
a) Write down the condition involving t for rays labeled 1 and 2 in the figure 3 to interfere constructively.
b) Write down the condition involving t' for rays labeled 2 and 3 in the figure to interfere constructively.
c) A particular application requires t = t' and uses light with wave length lambda = 600 nm in air. Combine your results from a) and b) to find the smallest value for t that satisfies both conditions.