Answer
a. The wavelength is 9.30 mm.
b. 4.65 mm.
c. $v= 2.05\times10^8m/s$.
Work Step by Step
a. The nodal planes of the magnetic field are $\lambda/2$ apart. We are told that distance is 4.65 mm, so the wavelength $\lambda$ is 9.30 mm.
b. Adjacent nodal planes of the electric and magnetic fields are the same distance apart, 4.65 mm.
c. $v=f\lambda=(2.30\times10^{10}Hz)(9.30\times10^{-3}m)=2.05\times10^8m/s$.