What Is The Difference Between These Dielectric Terms?

[FredericChopin]

What Is The Difference Between These "Dielectric" Terms?

Can someone please explain to me what the difference between these terms are?

1. Dielectric constant
2. Relative dielectric constant
3. Dielectric loss

I came across them on this website:

http://www.lsbu.ac.uk/water/microwave.html#pen

Also, I don't really know what "δ" and "ε_r'" on the website are meant to represent.

All and any help would be appreciated.

Thank you.

 

[FredericChopin]

Also, does anyone know the derivation to the equation:

$$\alpha = \frac{2 \pi }{ \lambda } \sqrt[]{ \frac{ \varepsilon_r \sqrt[]{1 + tan^{2} \delta } - 1}{2} }$$

, which is also on the website?

Thank you.

 

[NascentOxygen]

An ideal capacitor has no losses, a dielectric introduced between the plates just changes the total capacitance in proportion to the relative dielectric constant.

An non-ideal dielectric also introduces a loss, which we represent by a resistance between the plates. So the real capacitor shows both capacitance and resistance; I think that leads to the angle you have there, δ.