Graphical Portrayal of Electromagnetic Radiation
Copyright 2013, David Bryan Wallace
Warning! The ideas presented in this paper are at odds with Maxwell's laws and may be entirely wrong.
Graphic portrayals of electromagnetic waves in physics textbooks typically
[fig. 1] show a directed axis from which an array of vector arrows radiate in
two orthogonal planes ( plum )
intersecting in the axis. The
directed axis ( cyan )
represents the path and direction of propagation, vectors in one plane
represent electric field ( blue ), while the vectors in the other plane represent magnetic
field ( red ). Both fields vary sinusoidally along the
path with the two fields being in phase and, viewed from the source (not from
the destination) the magnetic field vectors are 90 degrees clockwise from the
electric field vectors. The
deficiencies of this portrayal become apparent when we consider two simple
cases of radio wave generation: a simple dipole transmission antenna and a
rotating dipole.
The Simple Dipole Transmission Antenna
The simple dipole transmission antenna [fig. 2, animated gif] can
be thought of as a piece of straight wire along which electric charge ( blue ) sloshes back and forth. Charge polarity alternates as does
current direction. The current ( green
) in the wire is zero when the separation of charge
is maximal, and the current is maximal when the separation of charge is
zero. Consequently, the generation
of electric ( blue ) and magnetic ( red ) fields is 90 degrees out of phase [fig. 3]. This wave pattern is characteristic of plane polarized
electromagnetic waves.
Circular Polarization
Circularly polarized electromagnetic waves can be generated by an
array of two dipoles skewed 90 degrees and spaced one quarter wavelength, or by
a rotating electric dipole (charge dipole, not antenna). The sense of polarization, or handedness
is called right handed (left handed) if the direction of rotation is clockwise
(counterclockwise) for an observer looking in the direction of
propagation.* A counter-clockwise
rotating dipole produces left circular polarized electromagnetic wave with
electric and magnetic field vectors parallel [Fig. 4]. On the other hand, a clockwise rotating
dipole produces right circular polarized electromagnetic wave with electric and
magnetic field vectors anti-parallel [Fig. 5].
*IEEE Std 149-1979 (R2008), "IEEE Standard Test Procedures
for Antennas". Reaffirmed December 10, 2008,
Approved December 15, 1977, IEEE-SA Standards Board. Approved
October 9, 2003, American National Standards Institute. ISBN
0-471-08032-2. doi:10.1109/IEEESTD.1979.120310, sec.
11.1, p. 61."the sense of polarization, or
handedness ... is called right handed (left handed) if the direction of
rotation is clockwise (counterclockwise) for an observer looking in the
direction of propagation"