听力原文:A heater is using convection when it warms the air in a room. And the air in turn warms the people and objects in the room. A hot water radiator, a stove and forced air furnace are all convection heaters. A quartz heater, on the other hand, heats the objects and people in a room without heating the air. It does this by producing radiation heat that travels like light waves. The radiation is then directed at objects by means of a reflector. How is the quartz heater different from other types of heaters?