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## Homework Statement

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.

## Homework Equations

## 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)