J.J.´s kinked tubes: EM radiation with scarcely a ∇in sight

Systems of tubes of force are a useful way of visualising electric or magnetic fields. Though they are generally associated with zero- or low-frequency problems, Sir J.J. Thomson extended their use to situations where it was necessary to think of tubes of force as having a propagation velocity. His `kinked tube´ analysis of a simple EM radiation problem provides a visual correlate to the existence of near and far components in the radiated wave