# RefractiveIndex.INFO

## Reflection coefficient

### Reflection coefficient

Would you provide more information on how the reflection coefficient has been calculated in the Refractive Index Info software. Is it based on the Fresnel equations, with the refractive index of material being a functionsof the wavelength?

Thanks

Lumi
lumiza

Posts: 1
Joined: Tue Mar 01, 2011 12:14 am

### Reflection coefficient

Hi Lumi,

yes, reflection is calculated at the specified wavelength using Fresnel equations

mikhail

Posts: 96
Joined: Sun Feb 08, 2009 12:00 pm

### Re: Reflection coefficient

If I understand correctly, the Fresnel equations are only valid for perfect insulators. The reflectance i get when using them for the metals listed does not match the shown values. However, if I include the extinction coefficient the numbers match at normal incidence. I'm not sure how to incorporate that term into the S-pol and P-pol equations though.
sensij

Posts: 1
Joined: Fri Apr 27, 2012 5:31 am

### Re: Reflection coefficient

Fresnel equations work in all cases, but you have to use complex refractive index n'=n+ik. In the case of oblique incidence all angles have to be treated as complex numbers too.

mikhail

Posts: 96
Joined: Sun Feb 08, 2009 12:00 pm

### Re: Reflection coefficient

How does it work? Can yo explain it with example?
AnaitaJones

Posts: 1
Joined: Mon Sep 10, 2012 12:08 pm

### Re: Reflection coefficient

Example: Aluminum at 0.6 microns

Real and imaginary part of the complex index of refraction from the database:
n = 1.26232
k = 7.1855

Complex index of refraction:
n' = 1.26232 + i*7.1855

Reflectance at normal incidence:
R = abs( (n'-1)/(n'+1) ) ^2 = 0.91103

See http://en.wikipedia.org/wiki/Fresnel_equations for the equations

mikhail