2條F.3 Phy 問題 22分 明天考試用!!

1. The two wrods "infrared" and "infra-red" are the same. But the word "infrared" is most commonly used.

2. It is because cold air is of higher density and thus sinks. The ice rack cools the air beneath it. When the air cools, it sinks to the down. Less cool air then rises and is cooled by the ice rack. Hence, a convection current is produced until the air inside the freezer chamber is cooled to a lower temperature.

If the ice rack is placed at the bottom, the air cooled by it only stays at the bottom. A convection current cannot produced. This would lower the cooling effectiveness of the freezer.

1. They are the same. No difference between meaning.
2a. The ice rack is placed on the top because ice rack produces cold air, and cold air will sink to the bottom of the freezer so that the food can be cooled.