Sodium vapor lamps are a type of gas discharge lamp that produces light by passing an electric current through sodium vapor. They are commonly used for street lighting and outdoor illumination due to their high efficiency and long lifespan. The light emitted is typically a yellow-orange color, which can be easily recognized. These lamps work by heating sodium metal until it vaporizes, creating a bright light when electricity flows through it. Sodium vapor lamps are known for their energy efficiency compared to traditional incandescent bulbs, making them a popular choice for urban lighting in cities and towns.