This document discusses various light sources used in spectroscopy and characterization instruments. It describes natural light sources like the sun and stars, and artificial sources like lamps, LEDs, lasers, and deuterium discharge lamps. Quartz tungsten-halogen lamps and LEDs emitting between 425-700 nm are commonly used visible light sources. Deuterium lamps emitting 180-370 nm and lasers are frequently used as ultraviolet sources. Nernst rods, globars, and hot wires or bulbs are mentioned as infrared sources. These light sources are used in applications like UV-visible spectroscopy, photoluminescence, FTIR, photo-catalytic reactors, and for studying material properties.