IB Physics TOK What did Planck Quantize?
/A tutorial sheet on the process of science in the development of quantum phenomena. See Physics Education, Nov 2000 p 381-386, A brief history of quantum phenomena by Gren Ireson.
- In 1900 Max Planck quantized the energy of the oscillators in the radiating body rather than the radiation from the body.
- Planck presented an argument that consisted essentially phenomenological curve fitting, relying on classical idea of entropy at long wavelengths and an ad hoc conhecture due to Wien for short wavelengths, but which fitted the data perfectly at all wavelengths. However he was unable to offer any theoretical justification for the results.
- Planck regarded the walls of the cavity as harmonic oscillators which could absorb and emit energy only in discrete amounts, E, which is related to the frequency, f, of the absorbed or emitted radiation by E = hf, where h is Planck's constant.
- In 1905 Albert Einstein took the notion of quantization further by suggesting that electromagnetic radiation exists in the form of packets of energy that we now call photons.
- Application of the photon model supplied Einstein with the means to solve the photoelectric effect. Classical electromagnetic theory predicted that the energy available in light is proportional to the intensity and independent of the frequency, but experimental evidence pointed to the opposite result.
