]> Fluorescence is a luminescence that is mostly found as an optical phenomenon in cold bodies, in which the molecular absorption of a photon triggers the emission of another photon with a longer wavelength. The energy difference between the absorbed and emitted photons ends up as molecular vibrations or heat. Usually the absorbed photon is in the ultraviolet range, and the emitted light is in the visible range, but this depends on the absorbance curve and Stokes shift of the particular fluorophore. Fluorescence is named after the mineral fluorite, composed of calcium fluoride, which often exhibits this phenomenon. The process by which a chemical species undergoes a chemical change as the result of the absorption of a photon of light energy. Continues to glow after light source is removed Radiation radiative process Glows when heated Glows when struck The radiance per unit wavelength or wavenumber interval. The electromagnetic (EM) spectrum is the range of all possible electromagnetic radiation. The electromagnetic spectrum (usually just spectrum) of an object is the characteristic distribution of electromagnetic radiation from that object. A radiometric term for the rate at which radiant energy in a set of directions confined to a unit solid angle around a particular direction is transferred across unit area of a surface (real or imaginary) projected onto this direction. Radiant energy per unit time passing some specified area from one side. In Raman spectroscopy, the depolarization ratio is the intensity ratio between the perpendicular component and the parallel component of the Raman scattered light. In radiation, the net flux of radiation into or out of a system. As a consequence of radiative forcing there must be some change to the nonradiative energy states of the system. Line-of-sight propagation refers to electromagnetic radiation or electromagnetic waves travelling in a straight line. The rays or waves are deviated or reflected by obstructions and cannot travel over the horizon or behind obstacles. Beyond that, material disperses the rays respectively the energy of the waves. Infrequently, any energy propagated by a physical quantity governed by a wave equation. LIDAR (Light Detection and Ranging) is an optical remote sensing technology that measures properties of scattered light to find range and/or other information of a distant target. The prevalent method to determine distance to an object or surface is to use laser pulses. Like the similar radar technology, which uses radio waves instead of light, the range to an object is determined by measuring the time delay between transmission of a pulse and detection of the reflected signal. LIDAR technology has application in archaeology, geography, geology, geomorphology, seismology, remote sensing and atmospheric physics.