The discussion revolves around the refractive index of materials specifically for radio waves, exploring how it varies with frequency across the electromagnetic spectrum. Participants inquire about the refractive indices of various materials at radio frequencies and the relationship between refractive index and permittivity.
Participants express differing views on the relationship between refractive index and permittivity, with some asserting a straightforward connection while others highlight complexities, indicating that the discussion remains unresolved.
There are limitations regarding the assumptions about frequency dependence and the specific materials being discussed, as well as the potential need for clarity on the frequency ranges of interest.
Also, can you please say what your target application is? What range of "radio" frequencies are you interested in? What kind of materials are you interested in? The better that you can ask your question, the better we can try to help you figure out the answers. Thanks.bbbl67 said:It's been stated that the index of refraction of materials varies with frequency throughout the EM spectrum. What are the index of refraction for various materials in the radio frequency?
Are radio refractive indexes just directly computed from their electrical permittivity? Optical refractive indexes don't seem to have such a straightforward relationship.tech99 said:The index of refraction (relative to vacuum) is the square root of the relative permittivity. For example, polystyrene, relative permittivity = 2.6 so refractive index relative to vacuum = sqrt 2.6 = 1.6 measured at 1 MHz.
Water, relative permittivity = 78 so index of refraction = sqrt 78 = 8.8 at 1 MHz.