Diagram of the electric fields (E) and magnetic fields (H) of radio waves emanating from a quarter-wave monopole radio transmitting antenna (small dark vertical line in the center). The diagram is a cross section of the three-dimensional radiation pattern, which is symmetrical about the vertical axis of the antenna (vertical dotted line). The lines are the electric field lines. The dots and crosses represent the magnetic field lines. The magnetic field lines are horizontal circles about the antenna axis, perpendicular to the plane of the drawing. The dots represent magnetic field lines emerging from the page, while the crosses are magnetic field lines entering the page. The E and H fields are perpendicular as implied by the phase diagram in the lower right. The electric and magnetic field patterns travel away from the antenna at the speed of light.