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1900

1905

Black Body spectrum and Emission-Absorption spectrum are "explained"

1913

1922

1923

Stern-Gerlach Experiment

  • Discover of the spin: another quantum property is demonstrated for the athom.

Compton Effect

  • Arthur Compton demonstrates light behavior is like particles' behavior: the concept of photon is confirmed

1924

Kinds of complementarity:

  • Position and momentum
  • Energy and duration
  • Spin on different axes
  • Wave and particle
  • Value of a field and its change (at a certain position)
  • Entanglement and coherence

1925

1926

1932

1935

1965

Flavia Marcacci

Chair History of Scientific Thought

Quantum Mechanics History

Before Planck

  • 1893: Wien's displacement (empirical) Law: for various temperatures, wavelength and maximum spectral radiance
  • 1900: Rayleigh-Jeans (Lord Rayleigh and James Jeans) Law: approximation to the spectral radiance of electromagnetic radiation of a black-body by classical approach. As a consequence, empirical data disapproved the theoretic predictions (ultraviolet catastrophe)

Max Planck Hypothesis: Nature is discrete

Wolfgang Ernst Pauli (1900 – 1958), Nobel 1945

Exclusion principle: two or more identical fermions (particles with half-integer spin) cannot occupy the same quantum state within a quantum system simultaneously

Planck's Law for Black Body

- B = Black body spectral radiation

Paul Dirac (1902-84)

Erwin Schrödinger (1887 – 1961) and Werner Heisenberg (1901–1976): two formal theories for the same physical theory

  • QM and SR
  • hypotheses of the anti-matter

- Schrödinger and the temporal equation for QM

Rutherford's athom

1927

1895

James Chadwick (Hughes Medal 1932, Nobel 1935)

Neutron Discovery

Niels Bohr and the atomic model

Discover of X-ray

Paradox and laws

Q.E.D.: QM and elementary particles

1935 Schrödinger's cat

1935 EPR paradox

QM applies to elementary particles (what happens inside a particle accelerator)

  • a new atomic model, based on the quantum hypotheses
  • Emission and absorption spectrum are explained
  • 1915: Sommerfeld modifies Bohr's model by the introduction of elliptic orbits

Thermodynamics

De Broglie dual hypotheses

for matter

Electromagnetism

  • Louis-Victor De Broglie (1892-1987, Nobel Physics 1929) suggests that particles of matter have properties wavelike. The wavelength is:
  • The particle's energy E is related to the frequency of its associated wave by the Planck relation:

Richard Feyman (1918-88), Sin-Itiro Tomonaga (1906-79), Julian Schwinger (1918-94)

(Nobel Physics 1965)

Solvay Congress 1927 (Leyden)

Volta Conference (Como, 11-27 Sept.)

Radioactivity and discovery of a subatomic world

Only Einstein believes in quantum hypothese

Copenaghen QM

  • Interpretation of the Wave Equation (De Broglie, Heisenberg, Schrödinger)
  • Complementarity Principle (Bohr: objects have complementary properties which cannot all be observed or measured simultaneously)

Geissler tube (1857)

1905: Photoelectric effect (Nobel 1921)

C - cathode assembly; the cathode itself is hot, and glows orange. It emits electrons which pass through the metal mesh grid (G) and are collected as an electric current by the anode (A) (from Wiki-source)

Complementary properties

Position and momentum

Energy and duration

Spin on different axes

Wave and particle

Value of a field and its change (at a certain position)

Entanglement and coherence[

Franck-Hertz experiment (1914, Nobel 1925)

First electrical measurement to clearly show the quantum nature of atoms (Bohr's model)

  • Emission of electrons (or other free carriers) when light is shone onto a material.
  • Photons like particles: light like discrete and localized quanta of energy

1926, principle of correspondence of Bohr

1925, principle of exclusion of Pauli: two electrons can never occupy the same quantum state.

1927, Heisenberg's principle of uncertainty.

1928, principle of Bohr's complementarity: the corpuscular and wavelike aspect of matter is never contradictory, because these aspects never come together.

Heisenberg Principle

Davisson and Germer

Heat capacity of solid (Eistein solid)

Experiment (1921 to 1925) to confirm De Broglie's hypotheses that particles' behaviour is wavelike.

Each atom is a quantum harmonic oscillator + same frequency for all the atoms

Heat capacity: amount of heat necessary to raise, or decrease, the temperature of a unit of mass of 1 K.

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