03/21/2014PHY 712 Spring Lecture 211 PHY 712 Electrodynamics 10-10:50 AM MWF Olin 107 Plan for Lecture 21: Continue reading Chap. 9 A.Electromagnetic waves due to specific sources B.Dipole radiation examples

03/21/2014PHY 712 Spring Lecture 212

03/21/2014PHY 712 Spring Lecture 213

03/21/2014PHY 712 Spring Lecture 214 Formulation of Maxwell’s equations in terms of vector and scalar potentials:

03/21/2014PHY 712 Spring Lecture 215 Electromagnetic waves from time harmonic sources

03/21/2014PHY 712 Spring Lecture 216 Electromagnetic waves from time harmonic sources – continued:

03/21/2014PHY 712 Spring Lecture 217 Forms of spherical Bessel and Hankel functions:

03/21/2014PHY 712 Spring Lecture 218 Electromagnetic waves from time harmonic sources – continued:

03/21/2014PHY 712 Spring Lecture 219 Electromagnetic waves from time harmonic sources – continued:

03/21/2014PHY 712 Spring Lecture 2110 Properties of dipole radiation field for kr >>1: B x y Example: z r  p E

03/21/2014PHY 712 Spring Lecture 2111 Example of dipole radiation source

03/21/2014PHY 712 Spring Lecture 2112 Example of dipole radiation source -- continued Relationship to pure dipole approximation (exact when kR  0)

03/21/2014PHY 712 Spring Lecture 2113 Alternative approach

03/21/2014PHY 712 Spring Lecture 2114 Alternative approach -- continued Linear center-fed antenna z r  d/2

03/21/2014PHY 712 Spring Lecture 2115 Alternative approach – linear center-fed antenna continued

03/21/2014PHY 712 Spring Lecture 2116 Alternative approach – linear center-fed antenna continued

03/21/2014PHY 712 Spring Lecture 2117 Dipole radiation in light scattering by small (dielectric) particles E inc H inc H sc E sc

03/21/2014PHY 712 Spring Lecture 2118 Dipole radiation in light scattering by small (dielectric) particles E inc H inc H sc E sc

03/21/2014PHY 712 Spring Lecture 2119 Estimation of scattering dipole moment: Suppose the scattering particle is a dielectric sphere with permittivity  and radius a:

03/21/2014PHY 712 Spring Lecture 2120 Scattering by dielectric sphere with permittivity  and radius a:  For E inc polarized in scattering plane: 

03/21/2014PHY 712 Spring Lecture 2121 Scattering by dielectric sphere with permittivity  and radius a:  For E inc polarized perpendicular to scattering plane:

03/21/2014PHY 712 Spring Lecture 2122 Scattering by dielectric sphere with permittivity  and radius a:  