Compton scattering

Please note that the photos were written in portuguese. However, there is much math which can be understood independently.

The debate in science about the nature of light (wave or particle) was one of the main issues discussed at the beginning of the 20th century. In 1905, Einstein gave the explanation for the photoelectric effect, in which he introduced the concept of photon (particle that constitutes light), which is absorbed by an electron in a metal plate, providing the energy needed to “eject” the electron from the metal surface. For the photoelectric effect, the corpuscular behavior of matter (particle nature) was demonstrated for light, differing from the wave behavior shown in Young's double slit experiment. In 1923 the concept of Compton scattering was proposed by physicist Arthur Holly Compton to explain the scattering of X-rays, caused by electrons. The scientist considered photons as particles, which hit an electron (in a type of inelastic collision), transferring part of its energy to the electron, causing it to retreat, while another photon, of less energy, longer wavelength and lower frequency, would be re-emited. In classical electromagnetism, the physical interpretation of the phenomenon can be understood as a wave of frequency f, which is absorbed by an electric charge, causing it to oscillate with a frequency f and then radiate photons of same frequency f. The variation in wavelength is called the Compton wavelength and quantifies how much the photon wavelength has varied (by comparing the incident photon of the scatter to the reemited photon). The Compton scattering model can only be applied efficiently to electrons that are considered free or approximately free (as when the incident radiation energy is much higher than the electron binding energies in the valence layer of atoms, which is, in a simple way , the energy that “holds” the electron to the atom). The interaction between light and matter is a single phenomenon (light interacting with matter), which varies in its description depending on the level of energy considered. For phenomena involving high energies, the so-called “pair production” is considered; for intermediate energies, Compton and Thomson scattering are applied. Finally, for low energies, the photoelectric effect is applied. The explanation of the Compton scattering earned the scientist the Nobel Prize in physics in 1927. The Compton scattering was a major advance for science because it demonstrated, as well as in the photoelectric effect, that light can show corpuscular behavior. In 1924 Louis de Broglie proposed the “de Broglie hypothesis”, in which he generalized the dual behavior (wave-particle) for matter.

Pictures 1 and 2: Compton scattering Photo 3: experiment carried out by Compton Photos 4 to 8: demonstration of the Compton equation Reference material: Physics for scientists and engineers volume 3 (Paul A. Tipler and Gene Mosca) http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/compton.html?fbclid=IwAR0BRujoUvWpJ0SA0ZpB9Q754ceHtTO_eXhtYBZQE_df4NIZcH8o5j0KSHA#c1