$2.$ A sinusoidal electromagnetic wave with frequency $7\mathrm{.}3$x$1015$Hz travels in vacuum in the $+$x direction. The amplitude of electric field is $1\mathrm{.}2$x$103$V$/$m$.$Find angular frequency w$,$ wave number k$,$ and amplitude of magnetic field. Write the wave function for the magnetic field in the formB $=$ Bmaxin $($ct $-$ kx$).$