Direct Effect: Why Does an Empty Dish in Microwave Feel Cool?
How is it possible for an empty plastic or glass dish in a microwave to feel cool while food on an adjoining dish is hot?
The phenomenon you're referring to is known as the "Direct Effect." Can you explain how this phenomenon occurs?
Explanation of the Direct Effect in a Microwave
When an empty plastic or glass dish is removed from a microwave oven, it can feel cool to the touch while the food on an adjoining dish remains hot. This is because microwaves heat food by directly exciting water molecules. When the microwave is turned on, the food absorbs the microwaves and heats up, while the empty dish does not contain any water molecules to absorb the microwaves. Therefore, the dish doesn't heat up as much as the food does. Additionally, the dish itself acts as an insulator, preventing the transfer of heat from the hot food to the dish. This insulation keeps the dish cool to the touch.
Detail Explanation of the Direct Effect
The Direct Effect phenomenon in a microwave occurs due to the way microwaves heat food. When you place food in a microwave-safe dish and heat it in the microwave, the microwaves cause water molecules in the food to vibrate and generate heat. This process heats up the food from the inside out, making it hot to touch once heated.
However, when you place an empty plastic or glass dish in the microwave, the dish itself does not contain water molecules to absorb the microwaves. As a result, the dish remains relatively cool to the touch compared to the hot food in the adjoining dish.
Furthermore, the plastic or glass material of the dish acts as an insulator, which means it is not as conductive as the food in absorbing and retaining heat. This insulation property of the dish prevents the transfer of heat from the hot food to the dish, keeping the dish cool even when the adjacent food is hot.
In summary, the Direct Effect occurs because the empty dish doesn't contain water molecules to absorb microwaves and the dish's insulating properties prevent heat transfer from the hot food, resulting in the dish feeling cool to the touch.