Hey guys, I was wondering if someone could explain to me when Thin Film Interference will produce constructive/destructive interference. I think I might understand it, but I'm not 100% sure and I have a test coming up soon. Any help would be great! Ok, so I know we have the equation: 2t = m[tex]\lambda[/tex] where t, is the distance the thickness of the film, and [tex]\lambda[/tex] is the wavelength. Say we have... ------- n1 ------- n2 ------- n3 Where n1 = air, n2 > n1 and n2 > n3. So then would the part of the ray reflecting off n2, have a 1/2 [tex]\lambda[/tex] phase change? But the ray reflecting off of n3 would undergo no phase change?? Would this produce destructive interference? What about when n2 > n1, and n3 > n2. I'm guessing that both the ray that reflects off n2, and off n3 would both undergo 1/2 [tex]\lambda[/tex] phase change, so this would be constructive? Or is it reversed?