Answer
a. 1.363 m.
b. 10.90 m.
Work Step by Step
a. The nodal planes of the magnetic field are $\lambda/2$ apart.
$$\lambda/2 =\frac{c}{2f}=\frac{3.00\times10^{8}m/s}{(2)(110.0\times10^{6}Hz)}=1.363m$$
b. We know $\lambda_n=\frac{2L}{n}$.
$$L=n\frac{\lambda}{2}=8(1.363m)=10.91m$$
