A magnetic field traveling wave of the form
is produced in the laboratory by two windings distributed in space such that the number of turns per unit length varies sinusoidally in space. The windings are identical except for a 900 separation. They are excited by currents of equal amplitude but 900 out of time phase. This is a linear version of Problem 4.10, which was cylindrical.
(a) If an observer is in an inertial frame traveling with speed V in the z-direction, what is the apparent frequency of the magnetic wave?