beam angle - The angle at which luminous intensity is 50 percent of the maximum intensity.bin - To sort or classify light sources (such as light emitting diodes) into groups according to their luminous intensity or color appearance.conduction - The process of removing heat from an object via physical contact with other objects or materials, usually metals.convection - The process of removing heat from an object through the surrounding air.cosine distribution - A property of a light source such that its luminous intensity in a particular direction is proportional to the cosine of the angle from the normal to the source.driver - For light emitting diodes, a device that regulates the voltage and current powering the source.heat sinking - Adding a material, usually metal, adjacent to an object in order to cool it through conduction.illumination - The process of using light to see objects at a particular location.indication - The process of using a light source as something to be seen as in signaling.junction temperature - For light emitting diodes, the temperature of the light-emitting portion of the device (see PN junction), which is inversely correlated with its light output.lumen maintenance - The lumens produced by a light source at any given time during its operating life as a percentage of its lumens at the beginning of life.monochromatic - For light, consisting of a single wavelength and having a very saturated color.PN junction - For light emitting diodes, the portion of the device where positive and negative charges combine to produce light.pulse-width modulation - Operating a light source by very rapidly (faster than can be detected visually) switching it on and off to achieve intermediate values of average light output; the frequency and the duty cycle (percentage of time the source is switched on) are important parameters in the modulation.semiconductor - A material whose electrical conductivity is between that of a conductor and an insulator; the conductivity of most semiconductors is temperature dependent.spectral power distribution (SPD) - A representation of the radiant power emitted by a light source as a function of wavelength.substrate - For light emitting diodes, the material on which the devices are constructed.tri-phosphor - A mixture of three phosphors to convert ultraviolet radiation to visible light in fluorescent lamps; each of the phosphors emits light that is blue, green or red in appearance with the combination producing white light.
