The electric field in an electromagnetic wave in vacuum is given by : $\vec{E} = (6.3 \text{ N/C}) [\cos (1.5 \text{ rad/m}) y + (4.5 \times 10^8 \text{ rad/s}) t] \hat{i}$ (a) Find the wavelength and frequency of the wave. (b) What is the amplitude of the magnetic field of the wave ? (c) Write an expression for the magnetic field of this wave.