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Forum: Processes Involving Optical Photons
Re: Question Question on reflectivity definition (Wenliang Li)
Date: 11 Oct, 2011
From: Gumplinger Peter <Gumplinger Peter>

Dear Wenliang Li,

The reflectivity of a dielectric_dielectric surface is calculated from Snell's Law. The empirical reflectivity you can enter with AddProperty("REFLECTIVITY" for dielectric_dielectric surfaces acts like a "dirty absorption" before Snell's Law even comes into play. With other words, reflectivity=1 (perfectly clean) is the default and what the photon does is determined by Snell's law alone (so, what is relevant are the index of refraction of the two media touching at that surface). If, on the other hand, you set reflectivity=0, the surface is so dirty that all photons are absorbed.

Please, note that for a glisur, polished surface, the G4OpticalSurface itself does not have an index of refraction (even, as in your case, you provided one). I think you mean to give the quarz the index you've given the surface. Only 'backpainted' surfaces in the UNIFIED model require their own refraction index - which in that case is the small gap layer.

I don't understand why you get for ref=0 all photons reflected. They should all be absorbed. For ref=1 photons will be refracted or reflected according to Snell's Law.

I suspect your problem is that you have not given the quarz of the finite thickness window an index of refraction. In that case, though, all photons should also be absorbed.

Peter

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1 Agree: Re: Question on reflectivity definition   (Wenliang Li - 17 Oct, 2011)
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