Johann Ritter is best known for his discovery of ultraviolet light in 1801. A year earlier, in 1800, William Herschel discovered infrared light. This was the first time that a form of light beyond visible light had been detected. After hearing about Herschel's discovery of an invisible form of light beyond the red portion of the spectrum, Ritter decided to conduct experiments to determine if invisible light existed beyond the violet end of the spectrum as well.