Answer to Question #32767 in Atomic and Nuclear Physics for DEVENDRA KHATIWADA
Was the concept of quantization present before the experiment performed by Robert MIllikan's?
Yes, for example J. J. Thomson's cathode ray tube experiments (discovers the electron and its negative charge) in 1897. In 1897, Thomson showed that cathode rays were composed of previously unknown negatively charged particleы, and thus is credited with the discovery and identification of the electron. Another example: the photoelectric effect that Einstein explained in 1905 (and later received a Nobel prize for it) using the concept of photons, particles of light with quantized energy. Only in 1909 was Robert Millikan's oil-drop experiment, which showed that electric charge occurs as quanta (whole units). Answer: Yes, J. J. Thomson's cathode ray tube experiments and Einstein’s photoelectric effect.