32. Electromagnetic Waves

The magnetic field of a travelling electromagnetic wave is described by the wave function $B(z,t)=1.0\times {10}^{-3}\sin (kz-1.27\times {10}^{12}t)$, where k is the wave number. Write the complete wave function for the electric field of this wave.

Electromagnetic waves produced by X-ray machines typically have a frequency of approximately $3.5\times {10}^{16}Hz$ . What is the wave number of these waves?