Index of Refraction: Find Coating & Thickness for 600nm Wavelength

[Nymn]

I'm stuck on a homework problem. It states the wavelength is 600 nm and the glass lens has an index of refraction of 1.40. Find the index of refraction for the coating and the required thickness.
I've googled around, but I'm not sure what equations I should be using. I got 1.183 for the coating (square root of 1.4) and 126.8 nm for the thickness. Is that right?

 

[sophiecentaur]

I'm stuck on a homework problem. It states the wavelength is 600 nm and the glass lens has an index of refraction of 1.40. Find the index of refraction for the coating and the required thickness.
I've googled around, but I'm not sure what equations I should be using. I got 1.183 for the coating (square root of 1.4) and 126.8 nm for the thickness. Is that right?

OK, where do you get the 126nm from and what reasoning did you use? Btw, I am not saying you're wrong at all. You can verify that you are right by just going over the 'λ/4 argument' and getting the reflection coefficient equal at both interfaces.