Week 14 Day 2 Spherical Waves Originates from a point source Total energy should be independent of radius of sphere Intensity decreases as 1 r No spread in wave energy Constant intensity Plane waves Conclusions For sinusoidal spherical waves Static charges with electric eld that diminish as 1 r do not radiate Charges moving at constant velocity also do not radiate Accelerating charges can radiate Types of Radiation Sinusoidal oscillations of charges in a metal wire lead to antenna radiation Impinging and stopping of a beam of electrons in a metal target gives rise to x rays of bremsstrahlung radiation Centripetal acceleration of electrons in a circular orbit leads to synchrotron radiation Concept Question Accelerating charges Correct answer 2 When you move a charge left or right it does not put a kink in the horizontal eld lines Radiation Atenna Accelerated charges are the source of EM waves Most common example os electric dipole radiation State of Polarization Describes how the direction of the electric eld in an EM wave changes at a point in space Linear polarization Circular polarization Elliptical polarization
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