I am really just not getting this. here is a homework problem.
A film of oil (n=1.25) floats on water (n=1.33). What is the thinnest film that produces a strong green reflection (wavelength = 500 nm).
And,2 about anti-reflection coatings on glasses.
A 90-nm thick coating is applied to a lens. What must be the coating's index of refraction to be most effective at 480 nm? Assume the coating's index of refraction is less than that of the lens.
If the index of refraction of the coating is 1.38, what's the minimum thickness the coating should be to be most effective at 480 nm?
None of the formulas given above include a term for index of refraction.
Is the idea that you figure ut which of the first two equations for delta-d to use, based on the index of refraction of the materials, and then substitute into one of the second two based on whether you're working with constructive or destructive interference?
I think in the first hw problem, both waves of shifted, since the air-oil-water sequence is always from low n to higher n. So, solve the equation 2t=500/1.25.
For the second, again both waves are shifted, but we're looking at destructive interference. So, 2*90=0.5*480/n ... and n = 1.33