33-5

An $LC$-circuit has a natural angular frequency oscillation given by

$$\omega=\frac{1}{\sqrt{LC}},$$

or in terms of regular frequency, we have

$$f=\frac{\omega}{2\pi}=\frac{1}{2\pi\sqrt{LC}}.$$

But, for an $EM$-wave we have $c=\lambda f$, or

$$c=\frac{\lambda}{2\pi\sqrt{LC}}.$$

So, solving for $L$ gives

$$L=\frac{1}{C}\left(\frac{\lambda}{2\pi c}\right)^2.$$

Putting in the numbers gives $L=5\times10^{-21}{\rm H}$, which is a very small value?