(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A thin film with a refractive index of n=1.50 is surrounded by air. Wavelengths of light 360, 450, and 602 nm are the only visible wavelengths missing from the reflected light. What is the thickness of the film.

2. Relevant equations

3. The attempt at a solution

One of the rays will be 180 degrees out of phase from the other so destructive interference should occur when:

2t = mλ'

So I tried:

2t = mλ'

2t = m(λ/n)

t = (1)(360/1.5)

t = 120 nm

But then I tried the same thing for another one of the given wavelengths:

2t = mλ'

2t = m(λ/n)

t = (1)(450/1.5)

t = 150 nm

For what is a seemingly simple problem I cannot see what I am doing incorrectly.

(the answer is 600 nm I just don't understand how to find it)

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# Homework Help: Interference due to a thin film

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