1. The problem statement, all variables and given/known data This question is question 5 from chapter 4 of Hecht's Optics, 4th edition. I found a pdf of the homework set, and the question is labeled as 4.5. http://www.physics.byu.edu/faculty/hess/471W09/Homework/Ch4.pdf" [Broken] 2. Relevant equations Not completely sure 3. The attempt at a solution I saw my professor for help with this problem, and he told me that we have to find the phase difference in between the incident ray and the transmitted ray (from glass to air). If there are any other important pieces of advice or hints or possible diving boards from which I can jump into this problem, I would greatly appreciate any help you can provide. Thanks!!!