Absorption – a process in which matter acquires photonic energy from electromagnetic radiation as wavelengths travel through or reflect off matter. additive lamp (bulb) – medium pressure mercury vapour lamp (arc or microwave) containing metal additives such as iron (Fe), gallium (Ga), lead (Pb), tin (Sn), bismuth (Bi), or indium (In). Additive lamps have UV spectral emissions that are different than those of standard mercury (Hg) lamps. Sometimes referred to as doped lamps or metal halide lamps. Adhesion – the bonding of an adhesive to an adherend (substrate) consisting of intermolecular forces, chemical bonds, and mechanical or interlocking interactions. The strength of adhesion is dependent on the adhesive, adherend (substrate) and cure. anode – positive terminal of a light emitting diode (LED). arc lamp – see mercury arc lamp arc length – distance between electrodes in a quartz lamp (bulb). See effective cure length. ASTM D3359 – ...