Old quantum theory

atomic model introduced by Niels Bohr in 1913

physical law that describes the amount of spectral radiance at a certain wavelength radiated by a black body cavity in thermal equilibrium

set of heuristic corrections to classical physics that served as a predecessor to modern quantum mechanics (1900–1925)

papers of Albert Einstein published in the Annalen der Physik scientific journal in 1905

energy-frequency relation in quantum mechanics

extension of the Bohr model to allow elliptical orbits of electrons around an atomic nucleus

principle of spectral lines