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 excites the mercury vapor, causing it to emit ultraviolet light. This UV light then interacts with a phosphor coating on the inside of the bulb, producing visible light.