Britannica Sources used in this answer

How do oscillating electrons in atoms scatter incoming light?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Diagram of a tree leaf illustrating photosynthesis, with arrows showing sunlight, water, and carbon dioxide entering the leaf and sugars and oxygen being produced. A person is shown beside the tree to demonstrate the exchange of oxygen and carbon dioxide between plants and animals. — electromagnetic radiation Diagram of photosynthesis showing how water, light, and carbon dioxide are absorbed by a plant to produce oxygen, sugars, and more carbon dioxide.

In the context of classical electromagnetic radiation, scattering occurs when the electric and magnetic fields of an incoming wave exert forces on an atom's bound electrons, forcing them to oscillate at the same frequency as the wave.12

Because these electrons are charged particles, their forced oscillation causes them to act as secondary sources of electromagnetic radiation. They effectively absorb energy from the primary wave as they are set into motion and then reradiate that energy as scattered light of the same frequency.12

The intensity of this scattered radiation is highly dependent on frequency, increasing with the fourth power of the frequency of the incoming light. This phenomenon, known as Rayleigh scattering, explains why the sky appears blue: higher-frequency blue light is scattered much more efficiently by atmospheric molecules than lower-frequency red light. When many such oscillators act in unison—such as in a solid—their secondary waves can interfere, leading to phenomena like reflection and refraction. While this classical model effectively describes many interactions, quantum effects become necessary to explain phenomena like Compton scattering, where light behaves as particles with discrete momentum.123