Which statement is TRUE with respect to halogen lamps?

Halogen lamps contain a fill gas that consists of halogen elements, such as iodine or bromine, which interact with tungsten molecules in a unique cycle known as the halogen cycle. This interaction is vital for the lamp's operation, as it helps to redeposit tungsten that evaporates from the filament back onto it, significantly extending the life of the bulb and maintaining light output.

This regeneration process occurs because when the tungsten evaporates, it forms tungsten halide compounds with the halogen gas. As the lamp operates and heats up, these compounds break down, depositing the tungsten back onto the filament instead of allowing it to coat the inside of the bulb. Therefore, the use of halogen as a fill gas plays a crucial role in ensuring the efficiency and longevity of halogen lamps.

Other options do not accurately describe how halogen lamps function. The mention of halogen being a coating or an inert gas does not align with the actual characteristics and operations of halogen lamps. Understanding the role of halogen fill gas is essential for grasping the advantages of halogen technology in lighting applications.