The noble gas commonly used in light bulbs is argon. Argon is a colorless, odorless gas that is inert, meaning it does not easily react with other elements. In incandescent and fluorescent light bulbs, argon is used to fill the space around the filament or the gas discharge to prevent oxidation. This helps prolong the life of the light bulb by preventing the filament from burning out too quickly. Argon's properties as a noble gas make it an ideal choice for lighting applications, and it is abundant in the Earth's atmosphere, making it readily available for industrial uses.