Mercury vapor lamps are a type of gas discharge lamp that produces light by passing an electric current through vaporized mercury. These lamps emit a bright, bluish-white light and are commonly used for outdoor lighting, such as streetlights and parking lots. They are known for their efficiency and long lifespan compared to traditional incandescent bulbs. The lamp consists of a glass bulb filled with a small amount of mercury and an inert gas. When electricity flows through the lamp, it ionizes the gas, causing the mercury to vaporize and emit ultraviolet light. This ultraviolet light then interacts with a phosphor coating inside the bulb, producing visible light.