Lecture 22 Ch 33

# Lecture 22 Ch 33 - PH 222-3A Spring 2007 222 3A...

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H 222- A Spring 2007 PH 222 3A Spring 2007 Electromagnetic Waves Lecture 22 Chapter 33 (Halliday/Resnick/Walker, Fundamentals of Physics 8 th edition) 1

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Chapter 33 Electromagnetic Waves oday’s information age is based almost entirely on the physics of Today s information age is based almost entirely on the physics of electromagnetic waves. Electromagnetic waves are at the core of many fields in science and engineering. In this chapter we introduce fundamental concepts and explore the properties of electromagnetic waves.
he wavelength/frequency nge which electromagnetic (EM) waves (light) Maxwell’s Rainbow The wavelength/frequency range in which electromagnetic (EM) waves (light) are visible is only a tiny fraction of the entire electromagnetic spectrum. Fig. 332 Fig. 33-1

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The Traveling Electromagnetic (EM) Wave, Qualitatively An LC oscillator causes currents to flow sinusoidally, which in turn produces oscillating electric and magnetic fields, which then propagate through space as EM waves. Next slide Fig. 33-3 g Oscillation Frequency: 1 LC ω
The Traveling Electromagnetic (EM) Wave, Qualitatively EM fields at P looking back toward LC oscillator 1. Electric and magnetic fields are always perpendiculartodirectioninwhich ave EB G G perpendicular to direction in which wave is traveling transverse wave (Ch. 16). 2. is always perpendicular to . GG yp p 3. always gives direc × G G tion of wave travel. 4. and vary sinusoidally (in time and space) and are (in step) with each other. in phase Fig. 33-4

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Mathematical Description of Traveling EM Waves Electric Field: ( ) sin m E Ek x t ω =− Wave Speed: 0 1 c με = Magnetic Field: ( ) sin m BB k x t = 00 μ All EM waves travel a c in vacuum Wavenumber: 2 k π λ = ngular frequency: 2 EM Wave Simulation Angular frequency: τ Vacuum Permittivity: 0 ε Vacuum Permeability: 0 Fig. 335 Amplitude Ratio: m m E c B = Magnitude Ratio: ( ) () Et c Bt =
A Most Curious Wave • Unlike all the waves discussed in Chs. 16 and 17, EM waves require no medium through/along which to travel. EM waves can travel through empty space (vacuum)! • Speed of light is independent of speed of observer! You could be heading toward a light beam at the speed of light, but you would still measure c as the speed of the beam!

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Lecture 22 Ch 33 - PH 222-3A Spring 2007 222 3A...

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