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www.GOALias.blogspot.comChapter EightELECTROMAGNETICWAVES8.1 INTRODUCTIONIn Chapter 4, we learnt that an electric current produces magnetic fieldand that two current-carrying wires exert a magnetic force on each other.Further, in Chapter 6, we have seen that a magnetic field changing withtime gives rise to an electric field. Is the converse also true? Does anelectric field changing with time give rise to a magnetic field? James ClerkMaxwell (1831-1879), argued that this was indeed the case – not onlyan electric current but also a time-varying electric field generates magneticfield. While applying the Ampere’s circuital law to find magnetic field at apoint outside a capacitor connected to a time-varying current, Maxwellnoticed an inconsistency in the Ampere’s circuital law. He suggested theexistence of an additional current, called by him, the displacementcurrent to remove this inconsistency.Maxwell formulated a set of equations involving electric and magneticfields, and their sources, the charge and current densities. Theseequations are known as Maxwell’s equations. Together with the Lorentzforce formula (Chapter 4), they mathematically express all the basic lawsof electromagnetism.The most important prediction to emerge from Maxwell’s equationsis the existence of electromagnetic waves, which are (coupled) timevaryingelectric and magnetic fields that propagate in space. The speedof the waves, according to these equations, turned out to be very close to