PHYSICS 1X00 Chapter 5.5: Chapter 5.5 Notes - The Electromagnetic Specturm
25 Apr 2018
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Electromagnetic waves were first postulated by james clerk maxwell and subsequently confirmed by heinrich hertz. Maxwell derived a wave form of the electric and magnetic equations, revealing the wave-like nature of electric and magnetic fields, and their symmetry. Because the speed of em waves predicted by the wave equation coincided with the measured speed of light, maxwell concluded that light itself is an em wave. According to maxwell"s equations, a time-varying electric field generates a magnetic field and vice versa. Therefore, as an oscillating electric field generates an oscillating magnetic field, the magnetic field in turn generates an oscillating electric field, and so on. These oscillating fields together form an electromagnetic wave. Maxwell also provided a method for calculating the theoretical speed of electromagnetic waves. Knowing two constants from his work in electromagnetic theory ( = electric permeability = 8. 85418782x10-12 c2/nm2, and = magnetic permeability = 4 x 10-7. N/a2), he could calculate the speed of an electromagnetic wave:
