I got a little confused of these three things by my teacher and Griffiths.

I am acquaintanced with Feynman's lectures on physics and what I get from there is [itex]\epsilon=\epsilon_{r}\epsilon_{0} = \left(1+\chi\right)\epsilon_{0}[/itex]

For some reason Griffiths, as well as my teacher, likes to use [itex]\mu_{0}[/itex], where [itex]\mu_{0} = \dfrac{1}{\epsilon_{0}c^{2}}[/itex].

Now I'd assume [itex]\mu=\dfrac{1}{\epsilon c^{2}}[/itex] and thus [itex]\mu=\dfrac{1}{\epsilon_{r}\epsilon_{0}c^{2}} = \dfrac{1}{\epsilon_{r}}\mu_{0}=\left(1+\chi\right)^{-1}\mu_{0}[/itex]

But apparently (Wikipedia, Griffiths, etc.) [itex]\mu=\left(1+\chi\right)\mu_{0}[/itex]

So what should it be?

And why do they use [itex]\mu[/itex] at all? It seem rather inconvenient to me, since they keep writing stuff like [itex]\sqrt{\dfrac{1}{\epsilon_{0}\mu_{0}}}[/itex] instead of c.

I am acquaintanced with Feynman's lectures on physics and what I get from there is [itex]\epsilon=\epsilon_{r}\epsilon_{0} = \left(1+\chi\right)\epsilon_{0}[/itex]

For some reason Griffiths, as well as my teacher, likes to use [itex]\mu_{0}[/itex], where [itex]\mu_{0} = \dfrac{1}{\epsilon_{0}c^{2}}[/itex].

Now I'd assume [itex]\mu=\dfrac{1}{\epsilon c^{2}}[/itex] and thus [itex]\mu=\dfrac{1}{\epsilon_{r}\epsilon_{0}c^{2}} = \dfrac{1}{\epsilon_{r}}\mu_{0}=\left(1+\chi\right)^{-1}\mu_{0}[/itex]

But apparently (Wikipedia, Griffiths, etc.) [itex]\mu=\left(1+\chi\right)\mu_{0}[/itex]

So what should it be?

And why do they use [itex]\mu[/itex] at all? It seem rather inconvenient to me, since they keep writing stuff like [itex]\sqrt{\dfrac{1}{\epsilon_{0}\mu_{0}}}[/itex] instead of c.

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