Thin film interference - Minimum thickness

[Saitama]

Homework Statement

A lens ($\mu$=1.5) is coated with a thin film of refractive index 1.2 in order to reduce the reflection from the surface at $\lambda=480 nm$. Find the minimum thickness of the film which will minimize the intensity of reflected. [Assume near normal incidence]

Homework Equations

The Attempt at a Solution

I don't really know how to begin with this. It looks to me that this is related to thin film interference but I have never dealt with three different mediums while solving problems related to this.

 

[Doc Al]

It looks to me that this is related to thin film interference but I have never dealt with three different mediums while solving problems related to this.

It's just thin film interference. All you need to worry about are the reflections from the top and bottom surfaces of the film.

 

[Saitama]

It's just thin film interference. All you need to worry about are the reflections from the top and bottom surfaces of the film.

Is it simply a plug and chug question then? :tongue2:

I get the right answer using the formula $2\mu d=(n+1/2)\lambda$ and putting $n=0$. I get $d=10^{-7} m$. Thanks Doc Al!