John Lekner is Emeritus Professor of theoretical physics at Victoria University of Wellington, New Zealand. After an M.Sc. at the University of Auckland and Ph.D. at the University of Chicago, he taught at the Cavendish Laboratory, Cambridge, where he was also Fellow and Tutor in Physics at Emmanuel College. He has worked in statistical physics, electromagnetism, quantum theory and theory of fluids. He is the author of 157 papers and of the books Theory of Reflection, 2nd Edition (Springer, 2016) and Theory of Electromagnetic Pulses (IOP Concise Physics, 2018).

• Preface.- Acknowledgments.- Fundamentals.- Beam-Like Solutions of the Helmholtz Equation.- Electromagnetic Beams.- Polarization.- Chirality.- Comparison of Electromagnetic Beams.- Sound Beams and Particle Beams.- Measures of Focal Extent.- Author's Biography.

John Lekner is Emeritus Professor of theoretical physics at Victoria University of Wellington, New Zealand. After an M.Sc. at the University of Auckland and Ph.D. at the University of Chicago, he taught at the Cavendish Laboratory, Cambridge, where he was also Fellow and Tutor in Physics at Emmanuel College. He has worked in statistical physics, electromagnetism, quantum theory and theory of fluids. He is the author of 157 papers and of the books Theory of Reflection, 2nd Edition (Springer, 2016) and Theory of Electromagnetic Pulses (IOP Concise Physics, 2018).

• Preface.- Acknowledgments.- Fundamentals.- Beam-Like Solutions of the Helmholtz Equation.- Electromagnetic Beams.- Polarization.- Chirality.- Comparison of Electromagnetic Beams.- Sound Beams and Particle Beams.- Measures of Focal Extent.- Author's Biography.