1801-1868

German mathematician and physicist who discovered cathode rays and the idea of spectrum analysis. Plücker's work with cathode rays led to the discovery of x rays by Wilhelm Röentgen in 1895. Today, cathode rays are used in most television sets and computer monitors (also called cathode ray tubes, or CRTs). Spectrum analysis is an important laboratory research tool, widely used by astronomers to classify stars and to determine their chemical composition.