Wave scattering is redistribution of an incident disturbance by an object or spatial variation in a medium. A small obstacle in a ripple tank redirects part of an incident water wave, and a variation of refractive index can redirect light. In a linear model, the total field is the sum of the prescribed incident wave and the outgoing scattered wave.
The scattered field carries information about the object's size, shape and material response relative to the wavelength. A far-field detector measures its angular distribution; the differential cross-section for scalar wave scattering compares scattered energy flux with incident energy flux. Wave scattering can remove power from a forward beam without wave absorption, because that energy can leave in other directions. Repeated encounters lead to multiple scattering. When interpreting a transmission experiment, collecting radiation over a larger angle helps distinguish redistributed power from genuinely absorbed power.
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