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Sorry if this is an easy question, I am new to physics and this field.

I have a question about reflectance which i believe to be "effectiveness of reflecting radiating energy"

My goal is to make a simulator that graphs the reflectance of a material at different frequencies of wave hitting it. However I am stuck on the equations

I have been looking through the fresnel equations and found no reference to wavelength in any of them. Moreover most examples seem to be for visible light which I'm not interested in (I will mostly be simulating in high GHz bands)

So, my question is:

Is there an equation where I can calculate reflectance for a given frequency and a given object (obviously the object would have different refractive index etc.)

Qmechanic
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Taylor
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1 Answers1

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Fresnel Equations work for RF/THz frequencies just fine (although they don’t include diffraction, which might also be relevant). The frequency dependence comes in through the material’s electromagnetic impedance, $\eta$. If it’s a non-magnetic material, you can use the refractive index, $n$, instead (which is probably what your reference uses). You need to find $n$ for the material and frequency of interest. Make sure you have the complete complex value!Then you plug it into the Fresnel Equations like usual.

In that frequency range, you might not find $n$ in the literature but instead find dielectric permittivity, $\epsilon$, or conductivity, $\sigma$. But that’s okay; you can convert from one to the other by using $$ n = \sqrt{\epsilon_r}, $$ where $\epsilon_r$ is the relative permittivity, and as described here.

Gilbert
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