Which of the following is also known as coherent scattering?

Which of the following is also known as coherent scattering?

• A. Photoelectric interaction
• B. Compton interaction
• C. Classical scatter
• D. Pair production

Answer: (C)

Coherent scattering is elastic scattering of photons by an atom, where the photon keeps essentially the same energy and the atom remains in its ground state. This is also described by classical wave theory, since the whole atom scatters the wave without transferring energy to the electrons, so it’s often called classical (or Rayleigh) scattering. The key point is that no ionization or energy transfer occurs and the phase of the wave is preserved, leading to scattering at small angles. In contrast, the other interactions involve energy transfer or absorption: the photoelectric effect absorbs the photon and ejects an electron; Compton scattering transfers part of the energy to a recoil electron, changing the photon’s energy and wavelength; pair production requires more energy than the photon has to create an electron-positron pair.

Coherent scattering is elastic scattering of photons by an atom, where the photon keeps essentially the same energy and the atom remains in its ground state. This is also described by classical wave theory, since the whole atom scatters the wave without transferring energy to the electrons, so it’s often called classical (or Rayleigh) scattering. The key point is that no ionization or energy transfer occurs and the phase of the wave is preserved, leading to scattering at small angles.

In contrast, the other interactions involve energy transfer or absorption: the photoelectric effect absorbs the photon and ejects an electron; Compton scattering transfers part of the energy to a recoil electron, changing the photon’s energy and wavelength; pair production requires more energy than the photon has to create an electron-positron pair.