Depict the variation of electric and magnetic fields in an electromagnetic wave as it propagates along z-axis. In a plane electromagnetic wave in free space, the electric field oscillates sinusoidally at a frequency of $1.5 \times 10^{10} \text{ Hz}$ with amplitude $36 \text{ Vm}^{-1}$. Find : (a) the wavelength of the wave, and (b) the amplitude of the associated magnetic field.