# Thin Film

1. Aug 6, 2008

### dragonrider

A material with an index of refraction of 1.44 is used to coat glass. The index of refraction of glass is 1.5. What is the minimum thickness of the coating that will minimize the reflection of light with a wavelength of 4680 A? Answer in units of µm.

I know that the thickness for this is t = λ/4ncoating

But I am not sure on how to find thickness when ncoating = 1.63

Last edited: Aug 6, 2008
2. Aug 7, 2008

The problem is with reflections at surfaces. You will get a different reflected wave when light reflects off of a higher index of refraction than on a lower index of refraction. I'll let you figure out what the difference is. It should be in your book. Also, I'm assuming that you know how you got your answer for t above when $$n_{coating}=1.44$$. If not then you'd better figure that out too.