to the final state 
it creates, effectively, an
electric dipole vibrating with angular frequency 
and the z component of the dipole moment is
given by
Problem session 7
Reviewed answers for problem set 6, especially how a full band accommodates an even number of electrons per atom. Bands in a ferromagnet. Viewed a periodic table with photos of the elements in their common state of aggregation: most are metallic. Showed how to convert numbers to binary and hexadecimal, manually and with convert(number, binary) in Maple. Also mentioned hexadecimal number basis.
Lecture 14, Mar 3
Demos: (1) disassembled tape player-radio: motor, magnetic head, ferrite antenna; (2) moving-coil loudspeaker and moving-magnet earphones; (3).microwave generator, interference of paths, metallic grating as a polarization filter.
Assigned readings: Bloomfield, sections 12.2 to 12.4; Serway, section 24.1 or equivalent (review); Melissinos, section 4.1;
Monochromatic plane wave solutions of Maxwell's equation. Linear, circular, elliptical and random polarization. propagating waves and standing waves. Electromagnetic energy and energy flux in a wave.
Lecture 15, Mar 5
Demo: linear, center-fed antenna: intensity and polarization.
Assigned readings: Melissinos, section 4.2; notes handed out (file antenna.tex).
Electric dipole radiation. Equivalence of a quantum transition to a
classical oscillating dipole: as the electron goes from the initial state
to the final state it creates, effectively, an
electric dipole vibrating with angular frequency and the z component of the dipole moment is
given by
Dipole scattering: intensity, angular distribution and polarization. Radiation from a half-wave center-fed linear antenna.
References: assigned readings.
Problem session 8
Discussed pledge homework solutions. Used PASCO interface to display sound waves and their spectra on oscilloscope.
Lecture 16, Mar 17
Phased antenna arrays and basic antenna designs. A Yagi antenna has, typically, one active element (connected to the power supply in broadcasting and to the TV set or radio in reception), and several passive elements, including a reflector and one or more directors, suitably spaced.
Fourier decomposition of a general periodic signal, emphasizing complex exponential formalism:
where T is the period and 
. Example of square
wave; behavior of Fourier series at a discontinuity of f(t)
(Gibbs phenomenon).
Assigned readings: Melissinos, section 3.1 and 3.2.
Lecture 17, Mar 19
Assigned problem set 8 (circuits, Fourier series).
Assigned readings: Melissinos, section 4.1; Bloomfield, sections 12.2 to 12.4; Serway, section 24.1 or equivalent (review);
General description of linear oscillations. Equivalence of driven, damped
mechanical oscillator with an electric circuit. Solution for the oscillator
driven at frequency 
, using the complex exponential formalism.
Phase coherence and incoherence in emission or scattering from an array (of emitters or scatterers). Diffraction. Incoherent scattering from density fluctuations in a medium: the blue of the sky. Coherent scattering in the forward direction leads to formation of the refracted wave, propagating with speed
(Note: this in SI notation, where 
and
. In the Gauss-cgs system there are no 
and 
to mess things up and one uses 
and 
to
denote 
and 
: the index of refraction is then 
and the speed is still it c/n)
Maxwell's equations in material media: a much simpler description of the formation of waves propagating with speed c/n.
References: assigned readings; Feynman, chapter 23, especially the
Table 23-1 on page I-23-6 (handed out). Note however that we use
, while Feynman uses 
Problem session 9
Given hints for the solution of problem set 8. Distributed MAPLE file fourier.mws and further discussed low-pass RC filter and low-pass RCL filter.
Lecture 18, Mar 24
Broad survey of emission spectra and the characteristics of emitted light (continued). Black-body spectrum. Actual emission spectrum of the sun. Cyclotron and synchrotron radiation. Electron accelerators as sources of synchrotron radiation. Polarization and coherence of light emitted from the sources discussed in the last two lectures. Coherence of laser light.
References: