32. Electromagnetic Waves

Electromagnetic waves produced by X-ray machines typically have a frequency of approximately $3.5\times10^{16}Hz$ . What is the wave number of these waves?

The magnetic field of an electromagnetic wave traveling along the z-direction is described by the wave function $B\left(z,t\right)=1.0\times10^{-3}\sin\left(kz-1.27\times10^{12}t\right)$, where k is the wave number. Write the complete wave function for the electric field of this wave.

(III) (a) When a circular parallel-plate capacitor is being charged as in Example 31–1, show that the Poynting vector →S points radially inward toward the center of the capacitor, parallel to the plates.