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Re: [Phys-l] g & E fields



Regarding:

Don't bite! This is a very deep question!
From the theoretical perspective, the intensity of the em wave is not
zero when the electric field is zero instantaneously. Why? The
magnetic field is in its maximum.

For the case of plane waves in vacuum, the electric and magnetic fields
are in phase with each other. When the electric field is zero, the
magnetic field is zero.

See, for instance, Classical Electrodynamics 2nd Edition, by John David
Jackson, page 271, where Jackson writes: "If [bold] n is real, (7.11)
implies that [script bold] E and [script bold] B have the same phase."
(Equation 7.11 reads: B = sqrt(mu epsilon) n x E where the n is printed
in boldface, the B and E are printed in script boldface, and the x is
the cross product symbol.)

In circularly polarized sinusoidal EM plane waves neither the electric field nor the magnetic field is zero anywhere at any time--they simply change direction in a helical manner while remaining mutually orthogonal to each other and to the wave vector direction. The Poynting flux is a global constant vector in space and time, and the EM energy density is also globally constant.

David Bowman