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## Homework Statement

A thin film of MgF2 with n = 1.38 coats a piece of glass. Constructive interference is observed for the reflection of light with wavelengths of 500 nm and 625 nm.

Part A -

What is the thinnest film for which this can occur?

## Homework Equations

t = lambda/2n *(m + .5)

and/or

lambda=(2*n*t)/(m+.5)

## The Attempt at a Solution

Not sure what I am supposed to do, because of the two wavelengths. I know what to do for a single wavelength...

So this is my work for solving the problem with each wavelength

m=0,1,2,3,...

500 = 2(1.38)(t)/(m+.5)

500(0+.5) = 2.76(t)

t = 90.6

and

625(0+.5) = 2.76(t)

t = 113

Now that I have done this, I am not sure how to proceed. Any help is appreciated.