Which material reflects microwaves?

Microwaves are a form of electromagnetic radiation that is commonly used in microwave ovens to heat food. The unique property of metals is their ability to reflect microwaves effectively. This is primarily due to their free electrons, which allow for the conduction of electric currents. When microwaves pass through or strike metal surfaces, these electrons move in response to the electromagnetic field, causing the microwaves to reflect instead of being absorbed.

In contrast, the other materials listed have different interactions with microwaves. Plastic, for example, can either absorb or transmit microwaves depending on its composition, and glass generally allows microwaves to pass through. Wood, being porous and composed of organic material, doesn't reflect microwaves effectively and is more likely to be penetrated by them, resulting in minimal microwave reflection. Understanding these interactions is crucial in contexts such as microwave oven design and food heating efficiency.