Scattering theory is a framework for studying and understanding the scattering of waves and particles. Raman spectroscopy relies upon inelastic scattering of photons, known as Raman scattering. Those include electron-positron annihilation, neutral pion decay, bremsstrahlung, inverse Compton scattering, and synchrotron radiation. Detectors relying on elastic scattering are called fast neutron detectors. Experimental tests of quantum electrodynamics are typically scattering experiments. It is a form of inelastic light scattering, where a photon excites the sample. A further application is in the characterization of particles by optical scattering measurements. An example is Compton scattering, with an electron and a photon undergoing elastic scattering. Organic matter influences the atmospheric radiation field by both scattering and absorption. This leaves emission of radiation from targets and scattering of neutrons. They are important in the physics of many processes, including particle scattering and Casimir forces. Propagation through heterogeneous media requires taking into account scattering. So it can come from changes of light reflection, absorption and/or scattering properties with temperature. Telescope sensitivity depends on observing time, optical bandpass, and interfering light from scattering and airglow. For energies far from the resonant energy the background scattering process dominates.