8.2 Double plate interference

Double plate interference

Assume that the normally incident light bounces off the bottom of the top glass and the top of the bottom glass. In this case there is a phase changebetween the two cases and the conditions of constructive and destructive interference flip.

So constructive interference occurs when $$2d=n\lambda /2n=1,3,5\dots$$ $$2x\alpha =n\lambda /2$$ or the position of the maxima are $$x_{max}=\frac{n\lambda }{4\alpha }n=1,3,5\dots$$

Destructive interference will occur at $$2d=n\lambda n=1,2,3,\dots$$ $$x_{min}=\frac{n\lambda }{2\alpha }n=1,2,3\dots$$