Sodium vapor lamps are a type of gas discharge lamp that produces light by passing an electric current through vaporized sodium. These lamps emit a characteristic bright yellow light, which is highly efficient and commonly used for street lighting and outdoor applications. The light is created when sodium atoms are energized, causing them to emit photons as they return to a lower energy state. There are two main types of sodium vapor lamps: low-pressure and high-pressure. Low-pressure sodium lamps are known for their monochromatic yellow light, while high-pressure sodium lamps produce a broader spectrum of light, appearing more white. Both types are valued for their energy efficiency and long lifespan.