# A Thin film refractive index determination

1. Oct 29, 2016

### sounouhid

Hi every one ,
I want to find the refractive index of a thin film using it's reflectance and transmittance spectrum
is there a way to do that ?

2. Oct 29, 2016

Normally, you already know the index of refraction of the thin film material, and the thickness of the film can be computed by observing the spacing of the peaks in the transmission vs. wavelength spectrum due to the Fabry-Perot effect. If I remember correctly $\Delta \lambda= \lambda^2/(2nd)$.

3. Oct 30, 2016

### sounouhid

Thank you
but my task is to find both the refractive index and the thickness of the film from these two measurements