點解金屬唔可以响微波爐度叮?

I suppose you ask why metal containers cannot be used in microwave oven.

Microwave is, in fact, electromagentic waves in nature. It composes of time varying electric and magnetic fields. The frequency used in domestic microwave oven is 2.45 GHz, similar to that used in Wi-Fi.

Metals contain a large amount of free electron. When microwave incident onto a piece of metal, the free electrons will oscillate under the action of the electric field component of the microwave. Part of the energy is thus absorbed by the electrons from the microwave, and the other is reflected. As a result, the microwave intensity decreases rapidly through the metal. This is why microwave normally cannot penetrate a piece of metal less than a millimetre thick.

If a food container is made of metal and is placed inside a microwave oven for heating, the microwave cannot penetrate through the metal container to reach the food. Under such situation, the food cannot be heated up.

Another point is that if there are sharp points on the metal container, charges will buld up at these points because of the action of the electric field of the microwave, sparks may produced from the accumulated charges.

因為微波所產生的頻率與金屬不相付..............