I Do materials have a refractive index for radio waves?

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The index of refraction for materials in radio frequencies is determined by the square root of their relative permittivity. For instance, polystyrene has a relative permittivity of 2.6, resulting in a refractive index of 1.6 at 1 MHz, while water, with a relative permittivity of 78, has an index of 8.8 at the same frequency. The discussion highlights that the index of refraction varies with frequency across the electromagnetic spectrum. Additionally, it emphasizes the importance of specifying the target application and frequency range for more tailored assistance. Understanding these refractive indices is crucial for applications involving radio waves.
bbbl67
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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?
 
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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.
 
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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?
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.
 
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.
Are radio refractive indexes just directly computed from their electrical permittivity? Optical refractive indexes don't seem to have such a straightforward relationship.
 
They do have but you need to use the permittivity value for the optical frequency and not the DC (or low frequency) one.
 
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