Chapters 39 and 40: Modern Physics

• Background: The main ideas about physics at the end of the 19th century. Concept of reference frame and the Principle of Galilean Relativity; The Galilean position and velocity transformations.
   
  
• Special Relativity: The concept of ether; The Michelson-Morley experiment (general idea and significance); The two postulates of Einstein's theory of special relativity; First consequences of the theory, relativity of simultaneity, length contraction and time dilation,

L = L_p/ γ ,   and   Δt = γ Δt_p ,   γ = 1/(1–v²/c²)^1/2 ,

where L_p is the proper length and t_p the proper time.

• Quantum Theory: The black-body spectrum and Planck's 1900 hypothesis; Einstein's 1905 work on the photoelectric effect and the existence of photons; Photon energy

E = hf ,   where h = 6.63 × 10^–34 J·s is Planck's constant .

The 1913 Bohr model for the hydrogen atom and de Broglie's 1923 postulate of a particle's wavelength, λ = h/p; Two-slit interference experiments with electrons. Complementarity and the wave-particle duality; The uncertainty principle, Δx Δp ≥ (1/2) h/2π.