OPTICS & OPTICAL PHENOMENA A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z                    HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site absorption The capture of photons by atoms, molecules, or ions, which results in a decrease in the intensity of light, or other electromagnetic radiation, as it passes through a substance. Absorption of electromagnetic radiation is the combined result of Compton scattering, σ, and photoelectric absorption, τ. If the intensity of the incident beam of radiation is I0, the intensity of the beam attenuated by absorption, If, may be written as: If = I0 e-μρt where t is the thickness of the absorbing medium and μ = σ + τ. In astronomy, absorption occurs, for example, in the atmospheres of stars, planets, and moons, and in the interstellar medium. Absorption in Earth's atmosphere is one of the causes of atmospheric extinction; between the stars it occurs as interstellar extinction. Absorption at a specific wavelength results in absorption lines or absorption bands; otherwise it is known as continuous absorption. Compare with emission. Related category    • OPTICS AND OPTICAL PHENOMENA Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP