The discussion focuses on calculating the transmissivity of reflective foils, specifically an infinitely thin gold foil that absorbs 1% of incoming radiation and emits 0.5% in both directions. The remaining 99% of the radiation is reflected, influenced by the foil's dielectric constant, as described by the Fresnel Equations. Participants emphasize the need to consider absorption, re-emission, and the thickness of the foil to achieve accurate results. Modifications to the model are necessary to account for the thermal effects of absorbed light, which alters the wavelength of re-emitted radiation.
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I am wondering what happens to the remaining 99% of the radiation after the first foil in your thought experiment. The reflection will depend on the Dielectric constant of the foil. See this link on Fresnel Equations.Christofer Br said:That is, transmission is 0.5%
It will be reflected, the foil is a conductor (lets assume it's gold because it has relatively constant emissivity across a very broad spectrum, exact properties are not important) - so it REFLECTED 99% and emitted additional 0.5% in one directionsophiecentaur said:I am wondering what happens to the remaining 99% of the radiation after the first foil in your thought experiment. The reflection will depend on the Dielectric constant of the foil. See this link on Fresnel Equations.
Just consider that all the light is either reflected or absorbed, and the absorbed light is immediately emitted equally in both directions perpendicular to the plane of the foil (thats why I insisted on an infinitely thin foil, so we can ignore emmisions from the "sides")sophiecentaur said:An "infinitely thin" foil is a bit too much of an abstraction for this question. Loads of light will pass through a thin enough gold foil. Just how thick are you suggesting?
You are assuming that the transmitted light is not relevant here then? I have a problem with that.Christofer Br said:Just consider that all the light is either reflected or absorbed, and the absorbed light is immediately emitted equally in both directions perpendicular to the plane of the foil (thats why I insisted on an infinitely thin foil, so we can ignore emmisions from the "sides")