The Lawrence tube is a form of picture tube for colour television, having a single electron gun, the beam from which scans the luminescent screen in horizontal lines, each line consisting of three closely spaced lines of three phosphors producing red, green and blue luminescence respectively. The beam is deflected to the line of appropriate colour by information contained in the signal waveform. Research Lawrence Tube
Luminescence is the emission of light as the result of any stimulus other than heat. If the stimulus is heat the emission of light is termed incandescence. Research Luminescence
Thermoluminescence is the luminescence produced in a solid when its temperature is raised. It arises when free electrons and holes, trapped in a solid as a result of exposure to ionising radiation, unite and emit photons of light. The process is made use of in thermoluminescent dating, which assumes that the number of electrons and holes trapped in a sample of pottery is related to the length of time that has elapsed since the pottery was fired. By comparing the luminescence produced by heating a piece of pottery of unknown age with the luminescence produced by heating similar materials of known age, a fairly accurate estimate of the age of an object can be made. Research Thermoluminescence
Barite or baryte is major ore of barium. It has a high specific gravity for a light coloured mineral and is a common gangue mineral in hydrothermal veins or as a replacement mineral in veins of limestone and dolomite. It is associated with lead, silver and antimonysulphides. It has the formulae BaSO4 and a relative hardness of 3. It was the first mineral to be found to be luminescent when heated, and led to the discovery of the luminescence of minerals. It is used as an ore of barium, for refining sugar, in the paper industry and as a pigment. Research Barite
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
Abbreviations
Research Lawrence Tube
