Introduction to Quantum Physics

Classical physics lost this argument in three separate places and each loss pointed the same way. The light from a hot object refused to follow the curve theory predicted, unless the energy of the vibrating charges came in whole bundles. Light falling on a clean metal surface would free electrons, but only if its frequency was high enough, however bright it was. And X-rays bounced off electrons as though they were particles, losing exactly the energy a particle collision would cost them. The blocks work through those three results in order, then follow the compromise that settled the matter, that every particle also has a wavelength and that position and momentum cannot both be pinned down at once.