The animation shows electric dipole radiation from
a quarter-wave antenna. The radiation generated by this antenna has a wavelength which
is equal to four times the the half-length of the antenna. Generally at the middle of
the antenna there is
a driving AC signal whose frequency is such that it produces light with a wavelength of four
times the half-length of the antenna or twice the full length of the antenna.
The motions of the field lines are in the direction
of the local Poynting flux vector.