Compton Experiment (or Compton Effect)

The famous Compton experiment concentrates on the wave rather than the particle aspect of quantum phenomena. It had been observed that the wavelength of ► X-rays is increased when they are scattered off matter. Arthur Compton (1892–1962) showed that this behaviour could be explained by assuming that the X-rays were photons (► light quantum). When photons are scattered off ► electrons, part of their energy is transferred to the electrons. The loss of energy is translated into a reduction of frequency, which in turn leads to a lengthening of the wavelength of the scattered photons. This happens because the relation E = h? = hc/λ holds. In these experiments, first carried out between 1919 and 1922, the scattering of X-rays is treated as a collision of photons with electrons (Fig. 1).