I've got two questions on anti-glaze coating. This is how I understand it: the phase difference between the light reflected by the front surface and the back surface of the coating is pi/2 so they would cancel each other out
1) Surely the two different path, one reflected off the front and the other from the back, aren't on top of each other. So why would they interfere? Is this just an approximation that's good enough?
2) This would destructively interfere the light reflected by the surfaces of the coating, but it may also be reflected off the back surface of the glass itself. Surely it wouldn't cancel out and still give reflection?