Dielectric constant refractive index relationship

[tomas632]

hi, i have seen on another topic here that the refractive index equals the square root of the dielectric constant. from datasheet values we have...

water refractive index = 1.333
dielectric constant = 80.1

Without even doing the calculation its obvious that the square root of 80.1 is not 1.333...im clearly missing something here, can somebody help me with this please?

Thanks

Tom

 

[Simon Bridge]

Look at the definition of the dielectric constant and the definition of the refractive index - find the relationship between these things and the speed of light.
http://en.wikipedia.org/wiki/Refractive_index#Dielectric_constant

 

[nasu]

Both dielectric constant and index of refraction depend on frequency.
When you write the relationship between them the values should be measured at the same frequency.
The value of about 80 is water's dielectric constant in DC regime or at very low frequency.
The 1.33 is the index of refraction at the frequency of visible light (about 10^14 Hz).

 

[drhassan]

in general the refractive index is equal to the sqrt(dielectric constant), but you have to notice the frequency dependence as mentioned by nasu (the previous Post)