Contents › Part 8

Part 8 — The Transition to Quantum Physics

1. Black-Body Radiation and Planck's Hypothesis
   • Cavity radiation and Kirchhoff's theorem
   • What classical thermodynamics could settle
   • The classical field theory and its failure
   • The measurements that decided the matter
   • Planck's law
   • What exactly was quantized
   • Out of the cavity: specific heats
   • The statistics behind the law
   • Black bodies in nature
2. The Photon: Photoelectric and Compton Effects
   • The photoelectric effect
   • The light-quantum hypothesis
   • Momentum and angular momentum of light
   • Compton scattering
   • Coincidence: the last classical alternative
   • The photon as a countable object
   • Creation and annihilation of quanta
3. Atomic Models and Spectra
   • Spectra before any model
   • The constituents of the atom
   • The nuclear atom
   • The Bohr model
   • The old quantum theory
   • X-ray spectra and the atomic number
   • Atoms in external fields
   • Levels made visible
4. Matter Waves
   • The de Broglie hypothesis
   • Electron diffraction
   • Interference of atoms and molecules
   • Neutron interferometry
   • How large can an interfering object be?
   • Wave packets
   • From a wavelength to a wave equation
5. Experiment: Franck–Hertz experiment
   • Historical context and the prediction under test
   • Apparatus
   • Procedure
   • Observations
   • Interpretation
   • Modern repetitions and precision
   • What the experiment settles
6. Experiment: The Blackbody Spectrum Measured experiment
   • Stefan: the fourth power, from Tyndall's data (1879)
   • Lummer and Kurlbaum: a black body one can build (1898)
   • Lummer and Pringsheim: Wien's law breaks (1899)
   • Rubens and Kurlbaum: residual rays in the far infrared (1900)
   • Radiometric realization of the kelvin (2019)
   • What the measurements settle
7. Experiment: The Photoelectric Effect and Compton Scattering experiment
   • Hertz and Hallwachs: ultraviolet light discharges a metal (1887–1888)
   • Lenard: the energy of the electrons ignores the intensity (1902)
   • Millikan: the slope of the line is $h/e$ (1916)
   • Compton: the wavelength of scattered X-rays changes (1923)
   • Bothe and Geiger: the two products appear together (1925)
   • Grangier, Roger and Aspect: a single quantum is not split (1986)
   • What the measurements settle
8. Experiment: Matter Waves Observed experiment
   • Davisson and Germer: electron diffraction by a crystal (1927)
   • Thomson and Reid: transmission rings from thin films (1927)
   • Estermann and Stern: helium and hydrogen diffracted (1930)
   • The electron double slit, one electron at a time (1961–1989)
   • Colella, Overhauser and Werner: gravity shifts a phase (1975)
   • Molecule interferometry and the edge of coherence (1999–2019)
   • What the measurements settle
9. Experiment: X-ray Spectra and the Charge of the Nucleus experiment
   • Röntgen: a new kind of rays (1895)
   • Barkla: characteristic radiation and the transversality of X-rays (1905–1911)
   • Friedrich, Knipping and von Laue: diffraction by a crystal (1912)
   • The Braggs: the reflection law and the X-ray spectrometer (1913)
   • Moseley: the high-frequency spectra of the elements (1913–1914)
   • Siegbahn: precision X-ray spectroscopy (1916–1925)
   • What the X-ray spectra established