Microwaves are primarily reflected by what material?

Microwaves are primarily reflected by metals due to their electronic structure and physical properties. Metals contain free electrons that can move easily, allowing them to interact with electromagnetic waves like microwaves. When microwaves encounter a metal surface, these free electrons oscillate in response to the microwave's electric field, which leads to reflection rather than absorption. This is why metal surfaces, such as the interior of a microwave oven, are effective at reflecting microwaves, ensuring that the energy remains contained within the cooking cavity and efficiently heats the food.

In contrast, materials like wood, glass, and plastic do not have the same capacity to reflect microwaves. These materials tend to absorb the microwaves to varying extents, which can lead to heating but not reflection. This absorption is due to the molecular structure and the lack of free electrons in these materials, which do not facilitate the same level of interaction with the microwaves as metals do. Thus, metals are the primary materials used in microwave applications for their reflective properties.