Hello, I am trying to understand thin film (in air) interference but I have a problem:(adsbygoogle = window.adsbygoogle || []).push({});

I know we have destructive interference when [itex]\delta=(2m+1)\pi[/itex].

Now i can try to calculate the thickness of the film to get it, so

since [itex]\delta =\frac{4nt\pi}{\lambda} - \pi[/itex] where t is the thickness,

I come to [itex]\delta=(2m+1)\pi=\frac{4nt\pi}{\lambda} - \pi [/itex]

that leads me to [itex] t=\frac{\lambda(m+1)}{2n} [/itex] instead of

[itex] t=\frac{m\lambda}{2n} [/itex]

(n is the refractive index and m is the integer parameter)

Where am I wrong?

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# Thin film interference formulae

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