Elastic scattering of electromagnetic radiation (light, X-rays, neutrons) can be used to determine the size of scattering particles. This results in a time-independent (static) signal, which has a noise component resulting from the Brownian, 1773–1858motion motion motion of the particles (dynamic). The frequency of the light is also changed by the motion of particles (Doppler-effect, quasi-elastic scattering). Radiation inactivation uses energy-rich electrons or neutrons to destroy molecules, the probability for hitting them is proportional to their size.