Question

Hey folks! I need your help with optics. In the below sketch, i need to find the optical path difference between the rays 2 and 3. I also need to find for which a the rays cancel each other out (destructive interferrence)? Help greatly appreciated !

Answer 1

my first thought would be that \[\Delta s = 4dn + 2an_0 + 0.5 \lambda \] with delta s being the difference, n the optical constant of the layers, n_0 being vacuum, 0.5lambda the phase shift.
This applies to vertical rays.