The birth of a new physics: the electron; electromagnetic waves; the special theory of relativity; the general theory of relativity. Quantum theory: the quantum hypothesis; the photoelectric effect; photons; the mechanics of minute particles. The nuclear atom: the structure of the atom; the Bohr Model of the atom; the quantum mechanical model of the atom; electron spin. Interactions of electromagnetic radiation and matter: the passage of radiation through matter; molecular spectra; fluorescence and phosphorescence. Nuclear physics: the structure of the nucleus; nuclear radiations; radioactivity; nuclear reactions and nuclear energy. Selected applications: the laser; the Mossbauer Effect; nuclear magnetic resonance; the conductivity of electricity through solids; invariance, symmetry and conservation laws.