The deflection of waves by obstacles or inhomogeneities, altering their direction and intensity.Wave scattering is the process by which waves—such as light, sound, or matter waves—are deflected, reflected, or diffused when they encounter an obstacle or inhomogeneity in their medium. This phenomenon is fundamental to many areas of physics, from the blue color of the sky (Rayleigh scattering of sunlight) to the way radar detects aircraft. Scattering can be elastic, where the wave's energy is conserved, or inelastic, where energy is transferred to the scattering object, altering the wave's frequency.
The study of wave scattering dates back to the 19th century, with Lord Rayleigh's explanation of why the sky is blue. The theory was further developed by Gustav Mie, who in 1908 provided a complete solution for scattering by spherical particles, now known as Mie scattering.
When a wave encounters an obstacle, it interacts with the material's properties, such as its refractive index or density. The wave's amplitude and phase are modified, and it radiates outward in new directions. The exact pattern of scattering depends on the size and shape of the obstacle relative to the wavelength, as well as the material's properties. For small obstacles, the scattering is often isotropic, while larger obstacles can produce complex angular patterns, such as the diffraction rings seen in X-ray crystallography.
Wave scattering is used in medical imaging (ultrasound), remote sensing (radar and lidar), and materials science (X-ray diffraction) to probe the structure of matter.
The phenomenon of 'Anderson localization' shows that in a disordered medium, waves can become completely trapped due to multiple scattering, turning a conductor into an insulator.
