#### RADLAB Seminar

# From Maxwell's Equations to Electromagnetic Waves: A Historic Appraisal

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To appreciate our full acceptance of the subject items, it is important to realize that the familiar equations referred to above bear little resemblance to those originally introduced by James Clerk Maxwell.

Maxwell introduced his equations in 1864. The inclusion of his radical concept of the “Displacement Current” in the set of equations led Maxwell to his famous conjecture that light is an electromagnetic wave.

Many in the existing scientific community found Maxwell’s equations difficult to understand. Maxwell died in 1879 without knowing the fate of his electromagnetic theory and his conjecture.

Later, his equations were modified and improved mainly by Hertz (in 1884) and Heaviside (in 1886) who gave us the scalar and vector forms, respectively, of Maxwell’s equations as we know them now. It was Hertz who in 1888 reported how he generated, radiated and received (in fact discovered) electromagnetic waves and also observed their optical properties. Thus, almost 25 years after his presentation, Maxwell’s theory and prediction were fully accepted by the scientific community.

It is appropriate to mention here that there were scientists and natural philosophers before Maxwell who speculated on the manner in which electric and magnetic effects are transmitted through space. There were also persons who before Hertz observed transmission of electromagnetic effects but could not explain them theoretically or experimentally.

The present talk will be a non-mathematical exposition of the fascinating story of Maxwell’s equations and electromagnetic waves which some consider to be the most significant scientific achievement of the nineteenth century.

Professor Dipak Sengupta received his B.Sc., Physics with honors in 1950, and his M.Sc., Radiophysics and Electronics (First Class), 1952.from Calcutta University, Calcutta, India. In 1958, he received his Ph.D., in Electrical Engineering, from the University of Toronto, Toronto Canada. Since 1953 Professor Sengupta spent years in teaching and research at various institutions including the years 1959-1986 at the University of Michigan Radiation Laboratory. Currently he serves as a Professor Emeritus in the Electrical Engineering, and Computer Science Department (Radiation Laboratory) at the University of Michigan and in the Electrical and Computer Engineering, at the University of Detroit Mercy, Detroit, Michigan. His areas of interest are: Antennas, Applied Electromagnetics, Plasmas, Scattering and Diffraction, Electromagnetic Interference, Electromagnetic Compatibility and Navigation Systems. His current research interest is the History of Electromagnetics and Electronics.