Answer:
767.2 nm
Explanation:
The optical path for the reflection for the inner surface is:
[tex]Path=2\times n_{film}\times thickness[/tex]
For maximum wavelength, this distance has to be traveled doubled (The ray is normally incident). So,
[tex]\lambda=4\times n_{film}\times thickness[/tex]
Given that:
[tex]n_{film}=1.37[/tex]
Thickness = 140 nm
So, wavelength is:
[tex]\lambda=4\times 1.37\times 140\ nm[/tex]
Wavelength is 767.2 nm
