Talk:Total refraction

I think that the negative refractive index is not a requirement. Optical impedance is defined as

$Z={\sqrt {\varepsilon /\mu }}$.

For total refraction impedances must match, i.e. $Z_{1}=Z_{2}$. If $\epsilon _{1}=-\epsilon _{2}$ and $\mu _{1}=-\mu _{2}$ then this condition is certainly fulfilled, but it is, obviously, not the only possible pair of numbers that satisfy the equation

${\frac {\varepsilon _{1}}{\mu _{1}}}={\frac {\varepsilon _{2}}{\mu _{2}}}$