ok this question is soo ambiguous.. isn't it obvious that one ray will be reflected with a phase shift of pi for the first air glass interface and the other will go pass the first interface and then get reflected from the second air glass interface with a pi phase shift.. and thus simply 2t=m(lambda).. ??
in comparison to these old tests 0177 has no ambiguity.. so is ETS revising their and improving their tests?? can i expect to get a test free from ambiguity this nov 7th ?