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## Homework Statement

A scientist notices that an oil slick floating on water when viewed from above has many different rainbow colors reflecting off the surface. She aims a spectrometer at a particular spot and measures the wavelength to be 750 {\rm nm} (in air). The index of refraction of water is 1.33

Now assume that the oil had a thickness of 200 \rm nm and an index of refraction of 1.5. A diver swimming underneath the oil slick is looking at the same spot as the scientist with the spectromenter. What is the longest wavelength lambda_water of the light in water that is transmitted most easily to the diver?

## Homework Equations

2t = (m+1/2)(λ/n) or 2t = m(λ/n) and of course, these depends on whether you want constructive or destructive. I think I want destructive because essentially, I want to know what wavelength I would see reflected. I think I have one phase change, so I would need the second equation more... I think.

## The Attempt at a Solution

the only math I have done is this: 2*200 nm * 1.33

I use m = 1 since that should give you the largest wavelength (I hope). ...It's not getting me the right answer.