THE+ATOM+helpful+diagrams

IB Physics > The atom =THE ATOM= Geiger and Marsden's experiment showed that the mass of the atom was concentrated ina small dense nucleus. Bohr realised that electrons circled the nucleus in certain discrete orbits. When an electron moves from one energy level to a lower one, it emits a photon with a characteristic frequency determined by the equation.

The different transitions between energy levels explain the hydrogen spectrum.

See various discharge lamps in this PHET simulation: Neon lights etc