hi ,i saw the relations that mu=n*z ,epsilon=n/z several times,but i don't know where them come from,and even where they can be used to.
So if here anyone know them ,please be kind to tell me .thanks in advance.
n is not equal to sqrt (e_r); you can simply see that by multiplying sides of both equations: mu*epsilon=n*z*n/z=n^2 => n=sqrt(mu*epsilon). So the correct equation is n = sqrt (e_r*mu_r); however, as mu_r is in most cases very close to 1, most of the times you can assume n=sqrt(e_r); but thats not always the case.