the real and imaginary parts of a complex number, as
in z = x+iy, with x = Re z
and y = Imz; the modulus (magnitude)
and phase of a complex number, as in 
with
Lecture 20, Apr 1
Shot noise: fluctuations in the average current due to the random arrival of electrons. Johnson noise: thermal fluctuations in the potential (effectively a white noise) and, as a result, current fluctuations (with a spectrum depending on the characteristics of the circuit). The Nyquist theorem. Relation between the power spectrum of current fluctuations and the current-current correlation function.
Assigned readings: Dorsey notes distributed last time and references therein.
Problem session 9
Reviewed problems from assignment 7: the blue of the sky and the red of the sunset; polarization of scattered radiation, Brewster's angle. Discussed how the inclination of the Earth's rotation axis determines the seasons.
Lecture 21, Apr 3
Assigned problem set 10 (nuclear potentials, nuclear reactions).
Distributed set of Dorsey notes: the next four lectures will follow these closely, with the addition of computer-based material (see next lecture). See these notes for additional readings.
Shown and discussed chart of nuclides. Distributed chart of the Standard Model of fundamental particles and interactions from CPEP (Contemporary Physics Education Project).
Lecture 22, Apr 8
Discussed features of the Standard Model with the help of the interactive computer program Particles from Lawrence Berkeley Laboratory, MacIntosh version, distributed by CPEP.
Problem session 10
Review of complex numbers, especially Euler's formula the real and imaginary parts of a complex number, as
in z = x+iy, with x = Re z
and y = Imz; the modulus (magnitude)
and phase of a complex number, as in with
the notion of complex conjugate 
;
the product of complex numbers and in particular 
and the inverse of a complex number, as in
Application to current-voltage relations in a circuit
(or part of it), with 
and
impedance
Simply, V = ZI and 
with
where 
is the resonant frequency of the circuit. The
time-average of the dissipated power is
Used this to solve problems 1 and 2 in Assignment 8.
Lecture 23, Apr 10
Assigned problem set 11, pledged (drills on complex numbers and complex impedance; nuclear and particle physics).
The effective nucleon-nucleon interaction is mediated,
mostly, by 
mesons: Yukawa potential. General relation between range
of the interaction and mass of the boson involved; the Compton length
Brief survey of cosmic rays: primaries colliding with nuclei in
the air generate showers of other particles, notably mesons that
decay into muons and their (undetectable) neutrinos.
Nuclear binding energies: the Weiszäcker formula. Examples of decays and
of nuclear reactions induced by neutrons and by 
particles.
References: Dorsey notes and (for cosmic rays) The Particle Explosion
Lecture 24, Apr 15
Used the Particle program to run an in-class (collective) quiz on nuclear and particle physics, answering the questions in the program. Laws of radioactive decay. Cross sections and mean free path.
References given in the Dorsey notes and the Particles program.
Problem session 11
Discussed problems from assignment 9 and handed out solutions. See file assign9.tex. Let students explore the Particles program, DOS version, on Physics Department PC's.
Lecture 25, Apr 17
Assigned problem set 12 (nuclear applications; the energy balance of the sun)
Nuclear reactors and nuclear bombs. The cooking of the elements in the sun and stars in general.
References given in the Dorsey notes.
Lecture 26, Apr 22
Demo: mousetrap simulation of fission bomb.
Report by Jonathan Rodney (in the group with Rodelle Benner, Ben Johnson, Michael Lyons) on medical imaging by MRI, radioactive nuclides, and PET. Further discussed magnetic resonance, in particular NMR.
Problem session 12
Discussed problems from assignment 11 (pledged). Reviewed use of complex
impedance: the resistance R is the real part of the impedance Z.
The time - averaged power is 
where I is the complex current. An elastic two-body collision is
simply described in the center of mass frame: the two particles approach
with momenta p and -p, and after colliding recede with
momenta 
and 
; the magnitude of is the same as the magnitude of p; in a head-on
collision 
, but in general
makes an angle 
with p and in the collision of two hard
spheres the probability is given by of an angle between and 
is 
(the probability
that is in the solid angle 
is simply 
)
Also given hints for problem set 12.
Lecture 27, Apr 24
Demo: precession of gyroscope as model of magnetic resonance.
Report by Beth Crimi (in the group with Matt Cowan, David Dorbad, Cindy Walters) on medical imaging by X-rays and ultrasounds. Course evaluations.
Lecture 28, Apr 29
Report by Fred Jones (in the group with Christian Beshara, Keith Gilbert, Cameron Pennington) on data transmission and quantum computing. Course summary.
Problem session 13
Distributed and reviewed the remaining assignments. Discussed possible sources of solar energy, other than nuclear, and how they are inadequate. Talked about origin of the universe and some cosmology.