How are electromagnetic waves produced by oscillating charges? Draw a sketch of a linearly polarized electromagnetic wave propagating in the Z-direction, indicating the directions of the oscillating electric and magnetic fields.
Solution
An oscillating charge is continuously accelerating, so it produces an electric field that varies with time; this changing field generates a changing magnetic field, which regenerates the electric field, and so on. The coupled, self-sustaining fields detach from the charge and travel outward as an electromagnetic wave at the frequency of oscillation. For a linearly polarized wave along z the electric field stays confined to one plane, e.g. Ex=E0sin(kz−ωt), with By=B0sin(kz−ωt) perpendicular to it; the sketch shows E oscillating along x and B along y, with propagation along z.
