In the chapter about transmission lines, there was the following question: Given a frequency of 1GHz and a relative permittivity of 2.25, what is the wavelength of the sinusoidal wave?
In an unofficial solution they do the following:
$$c = \frac{1}{\sqrt{\mu\epsilon}} = \frac{1}{\sqrt{\mu_0\epsilon_0 \cdot \epsilon_r}} = \frac{3\cdot10^8}{\sqrt{2.25}} = 2 \cdot 10^8 = \lambda f$$
Which results in a wavelength of $0.2m$. The fact that this solution equals the numerical solution given by our prof makes me believe that this is the right method. There's one thing I don't understand, why can you write $\sqrt{\mu\epsilon} =\sqrt{\mu_0\epsilon_0 \cdot \epsilon_r}$?
Any help is really appreciated, thanks!
