Undergraduate course, Department of Physics, Gyeongsang National University
A companion to Sang Hoon Lee's lecture notes on S. T. Thornton, A. Rex, and C. E. Hood, Modern Physics for Scientists and Engineers (5th ed.). Each chapter pairs the lecture notes with simulations and calculations that run live in your browser.
Planck vs Rayleigh–Jeans, at a slowly changing temperature
Spectral intensity 𝓘(λ, T)
Total power R(T), log–log
The temperature sweeps between 2500 K and 10,000 K. Planck's law (blue) peaks at λmax = 2.898 mm·K / T, which slides through the visible band as the body heats up; the classical Rayleigh–Jeans formula (orange) agrees at long wavelengths but blows up at short ones, the ultraviolet catastrophe. On the right, the numerically integrated spectrum (dots) follows the Stefan–Boltzmann law σT⁴. Explore it yourself in Chapter 3, §3.5.
Inertial frames and Galilean invariance, the ether and the Michelson–Morley experiment, Einstein's postulates, the Lorentz transformation, time dilation, and length contraction.
Demos: the Michelson–Morley interferometer, two flashes and two observers, Galilean vs Lorentz wavefronts, two light clocks on one ship, a trip to Alpha Centauri, what a moving object looks like.
Velocity addition, experimental tests, the twin paradox, spacetime diagrams and the invariant interval, the relativistic Doppler effect, relativistic momentum and energy, and electromagnetism and relativity.
Demos: Galileo vs Einstein velocity addition, muons reaching the ground, two events in any frame, the twin paradox in spacetime, the Doppler effect for light, momentum bookkeeping, accelerating electrons, a wire seen from two frames.
X rays and the electron, Millikan's oil drops, hydrogen line spectra, quantization, blackbody radiation and Planck's constant, the photoelectric effect, x-ray production, the Compton effect, and pair production and annihilation.
Demos: Thomson's e/m experiment, a simulated oil-drop experiment, the hydrogen series, Planck vs Rayleigh–Jeans, the photoelectric experiment, the x-ray continuum, Compton scattering, pair production in a magnetic field.
The Thomson and Rutherford models, Rutherford scattering, the collapse of the classical atom, the Bohr model and the correspondence principle, reduced mass and hydrogen-like ions, characteristic x rays and Moseley's law, and the Franck–Hertz experiment.
Demos: α particles meeting a nucleus, a Geiger–Marsden experiment by Monte Carlo, the death spiral of a classical atom, energy levels and transitions, quantum jumps approaching classical orbits, Moseley's law, the Franck–Hertz experiment.
X-ray diffraction and Bragg's law, de Broglie waves, electron diffraction, wave packets and group velocity, wave–particle duality and the double slit, the uncertainty principle, the probability interpretation, and the particle in a box.
Demos: single-electron double-slit buildup, Bragg reflection, a standing wave around the orbit, a de Broglie wavelength calculator, the Davisson–Germer peak, building a wave packet, phase and group velocity, the double slit with a which-slit detector, uncertainty, standing waves in a box.
The Schrödinger equation, normalization and stationary states, expectation values and operators, the infinite, finite, and three-dimensional square wells, the harmonic oscillator, and barriers and tunneling.
Demos: a wave packet tunneling (live Schrödinger solver), probability as area, the infinite square well and a sloshing superposition, bound states of a finite well, degeneracy in a box, the quantum harmonic oscillator, barrier transmission, the STM.
The Schrödinger equation in spherical coordinates, quantum numbers and space quantization, the normal Zeeman effect, the Stern–Gerlach experiment and intrinsic spin, selection rules, and electron probability densities.
Demos: cycling orbital densities, space quantization of L, counting the states of level n, the normal Zeeman effect, the Stern–Gerlach experiment, allowed and forbidden transitions, an orbital explorer for any (n, ℓ, m).
The Pauli exclusion principle and the periodic table, shielding and ionization energies, Rydberg atoms, total angular momentum and spin-orbit coupling, Hund's rules, LS and jj coupling, term symbols, and the anomalous Zeeman effect.
Demos: electrons filling subshells, an interactive periodic table with ionization energies, Rydberg atom sizes, adding L and S, term symbols for two electrons, normal and anomalous Zeeman patterns.
The Maxwell velocity and speed distributions, equipartition and heat capacities, classical and quantum statistics, the Fermi electron gas and electrical conduction, and Bose–Einstein statistics: blackbody radiation, superfluid helium, and particle exchange symmetry.
Demos: a colliding gas relaxing to the Maxwell distribution, degrees of freedom switching on, the Maxwell speed distribution, counting configurations of two particles, three distribution functions, counting states in number space, the Fermi gas at finite temperature, Bose condensation, symmetric and antisymmetric two-particle wave functions.
All pages work on phones, tablets, and desktops, in light and dark mode. Animations are deliberately slow and can be paused.
Created by Claude Opus 5.5 (Anthropic) based on Sang Hoon Lee's lecture notes, for the undergraduate course Modern Physics (현대물리학) of the Department of Physics, Gyeongsang National University.