High-pressure Mercury lamp is a vapor or gaseous discharge lamp that uses Mercury in an excited state to produce light. Arc discharge takes place in a transparent tube inside a larger bulb of glass. The outer bulb reduces the ultraviolet radiation of the inner arc tube. Radiation from the Mercury arc is confined to four specific wavelengths in the visible range and several strong lines in the ultraviolet. This lamp is a very important source of ultraviolet radiation to many industrial and research applications. LLE-9 is specially designed as a lab instrument.